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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 1522
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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I have a 94 SL500, was low on gas and on the way to the

Customer Question

i have a 94 SL500, was low on gas and on the way to the station it started to loose power, pushing down the gas peddle almost to the floor kept it running for 100 yards but then it died. It cranks but won't start, I can almost start it by pressing the gas pedal to the floor but after 20 seconds it of cranking and almost starting it dies. I checked fuel pressure during cranking and its at 50 to 60 PSI. Checked to see if I had spark and it does. if I have spark and fuel then thought oxygen could be the problem. I have ordered a new Oxygen sensor along with new CPS's. The CSP's arrived without the O2 sensor. I installed the CSP's but still won't start. should get the O2 sensor today but I'm not optimistic. Any help would be appreciated.
Submitted: 11 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 11 months ago.

hello, so how is the flow of fuel ? does it come out of the fuel rail at a good rate of flow?

Customer: replied 11 months ago.
I haven't done any visual inspections of the fuel flow. I have a pressure gauge and assumed the flow would be adequate if the pressure was nearly 60PSI. How should I test this, remove an injector?
Expert:  Lou P. master tech replied 11 months ago.

no, does your fuel gauge have a button to release the pressure? if you do then hold the button down to allow fuel to flow out and into a bucket of sorts, and crank the car while holding to see how much flow comes out. pressure is not relative to flow.

Customer: replied 11 months ago.
It does have a pressure release button and attached tube. Let me do that test and I will be back with you. I need a few minutes.
Expert:  Lou P. master tech replied 11 months ago.

ok let me know. :)

Customer: replied 11 months ago.
I tested it with the release button pushed. The pressure remained at 40 psi through cranking and pushed about 2 to 3 oz of gas
Expert:  Lou P. master tech replied 11 months ago.

ok, do you have starter fluid to spray to see if it will start with starter fluid?

Customer: replied 11 months ago.
I tried that and it does not work.
Customer: replied 11 months ago.
I didnt want a call just the next suggestion.
Expert:  Lou P. master tech replied 11 months ago.

Ok so the car does not start off of starter fluid ?

Customer: replied 11 months ago.
It does not start when I spray starter fluid in the MAF
Expert:  Lou P. master tech replied 11 months ago.

Ok then you have no spark. BUT just to re confirm. You ran out of gas then put gas in it. And then this happened Right?

Customer: replied 11 months ago.
no, I didn't run out of gas, the reserve light had not yet turned on. Also, I have checked to see if I have a spark by pulling off one of the wires to one of the cylinder plugs and putting a new plug into the loose wire that is still connected to the distributor. It sparks on a regular interval.
Expert:  Lou P. master tech replied 11 months ago.

Ok well if the car does not run off of starter fluid then that tells me the spark is not enough or the plugs are fouled. I suggest remove a few plugs and check for wetness on them after trying to start it about 4 times. If it does not run on starter fluid then we're after spark.

Customer: replied 11 months ago.
Ok, I'm on it. I will let you know shortly.
Customer: replied 11 months ago.
the plugs are moist with gas.
Customer: replied 11 months ago.
The plugs were changed less than one month ago, so they are not coated with excess carbon.
Expert:  Lou P. master tech replied 11 months ago.

Ok so we know we are at least getting gas. So it's one of two things. Weak spark or bad gas. So clean all the plugs. Then while they are out. Crank the engine a few seconds so it clears the cylinders. Then put only one plug into the wire or coil and lay it against the block to see if it sparks wen it cranks. If it does then reinsert the plugs and see if it starts.

Customer: replied 11 months ago.
should I do this for all 8 cylinders?
Expert:  Lou P. master tech replied 11 months ago.

Yes. Tedious I know lol but it needs to be Done

Customer: replied 11 months ago.
ok
Expert:  Lou P. master tech replied 11 months ago.

Ok

Customer: replied 11 months ago.
Done. Each plug sparked. after doing all 8 it still won't start. it doesn't get close to starting until I floor the gas pedal and one time it started for 2 seconds then after that it would only get very close to starting but doesn't.
Expert:  Lou P. master tech replied 11 months ago.

ok, so what happens when you floor it is the computer actually cuts out fuel delivery , so your gas may be the issue., go ahead and pull out just one plug and check it. see if its wet

Customer: replied 11 months ago.
it is wet.
Customer: replied 11 months ago.
I actually pulled 2 plugs and both are wet, one is clean gas and the other looks dirty, not the color of oil but dark.
Expert:  Lou P. master tech replied 11 months ago.

ok so i think we have a fuel issue, do you know where the fuel pump relay is at?

Customer: replied 11 months ago.
I do. In fact I changed the fuel pump and canister filter 20K miles ago. I didnt touch the filter that is part of the fuel drain plug though and I have never drained the fuel tank of any sediment.
Expert:  Lou P. master tech replied 11 months ago.

ok so pull the fuel pump relay out.

Customer: replied 11 months ago.
ok its out
Expert:  Lou P. master tech replied 11 months ago.

ok now crank the car and verify no fuel pressure at the rail

Customer: replied 11 months ago.
there is still 58PSI at the rail
Expert:  Lou P. master tech replied 11 months ago.

then the fuel pump relay was not pulled. is it green? ill check the location, if it is pulled then bleed it of with your tool and see if it comes back up.

Customer: replied 11 months ago.
its green with a 30amp fuse in the top. it is located behind the bank of fuses for the rest of the electrical system. I did bleed the pressure gauge and it came up to 58 psi again. I will repeat and see if it is the same
Expert:  Lou P. master tech replied 11 months ago.

ok its on the passenger side of the trunk behind the panelling is what i am seeing, near the battery

Customer: replied 11 months ago.
same result is there another relay somewhere? here is a pict of the relay I have pulled
Expert:  Lou P. master tech replied 11 months ago.

that is the one. and you still have fuel pump activation?

Customer: replied 11 months ago.
apparently so.
Customer: replied 11 months ago.
what next?
Expert:  Lou P. master tech replied 11 months ago.

ok sorry, disconnect the fuel pump(s)

Expert:  Lou P. master tech replied 11 months ago.

what we need to do is stop fuel flow so we can see if the car will run off of starter fluid. or let me see if there is a fuse for the fuel injectors.

Expert:  Lou P. master tech replied 11 months ago.

ok there is no fuse, so either unhook the fuel pump grounds or unplug all the injectors, i think we may be working with bad gas

Customer: replied 11 months ago.
I unplugged all of the fuel injectors then sprayed some starter fluid in the MAF and it started for 1 second and as I crank it almost starts like it did before when I was flooring the gas pedal. the fuel gauge still reads 60psi in the rail. What do you think?
Expert:  Lou P. master tech replied 11 months ago.

Ok so do you have someone to help to keep spraying starter fluid little at a time so to see if it keeps running ?

Expert:  Lou P. master tech replied 11 months ago.

And also I want you to get a fuel sample into a glass jar. And let it set and see if it separates. I think you have bad fuel.

Customer: replied 11 months ago.
unfortunately it doesn't start when I have someone crank it while I squirt starter fluid in. I am trying to get the sample of gas now. I assume you want it directly from the tank, right. Not from the pressure gauge after it has been filtered.
Expert:  Lou P. master tech replied 11 months ago.

No from the Guage is fine water will not filter in the filter.

Customer: replied 11 months ago.
The gas is mostly the same constancy (viscosity), but at the very bottom their is a 1/32 of an inch that is another layer. Does water appear at the top or bottom?
Customer: replied 11 months ago.
I have a 1/2 bottle of SeaFoam. should I pour that in or simply drain the tank and put fresh premium in?
Expert:  Lou P. master tech replied 11 months ago.

Gas floats on water. That is water. That is the issue. You will need to drain the tank. Then clean or replace the plugs and fill with fresh fuel and some heet additive. That's the issue my man. Good work !

Customer: replied 11 months ago.
got it! Thank you!
Expert:  Lou P. master tech replied 11 months ago.

No problem ! Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! 😉

Customer: replied 11 months ago.
I am draining the tank now but I want to be sure I understand. i have about 6 oz of gas in a glass. at the bottom of the glass their is 1/32 of an inch that appears to be a clear but separate liquid. i am sure i don't have 5 and 3/4 oz of water and a small bit of gas. if water floats I don't think this is water. I will let you know how things go after I purge the old gas and replace with treated gas.
Expert:  Lou P. master tech replied 11 months ago.

No it's gas at the top and water at the bottom.

Expert:  Lou P. master tech replied 11 months ago.

Either that or you have a mixture of gas and diesel

Expert:  Lou P. master tech replied 11 months ago.

And just because it's separated in the glass does not mean it separated in the tank it will mix and that's what will cause the engine to not run and the plugs be soaked

Customer: replied 11 months ago.
I drained the tank, put 10 gallons of Premium chevron gas with a 1/3 bottle of Sea Foam and then cranked it and pressed the release value on my pressure gauge and ran a half a quart through into a bucket, cleaned all the plugs and tried to start it. It tried to start but only if I press the pedal to the floor. I ran some more gas into a cup to make sure no water or other was in the gas and it looks clean but still won't start. Any thoughts?
Expert:  Lou P. master tech replied 11 months ago.

yes, your car is the devil, no seriously, let me think on this a sec.

Expert:  Lou P. master tech replied 11 months ago.

you plugged the fuel injectors back in correct?

Expert:  Lou P. master tech replied 11 months ago.

and you probably need to check the plugs once again to make sure., now that we have fresh fuel , if the plugs are wet we know we have a spark issue. we can have spark but it be weak , you should have individual coils so its hard for me to believe we have a spark issue, but we need to rule that out, man i was for sure we had a fuel issue. sorry for the time spent .

Customer: replied 11 months ago.
Ok, I need to run some errands. Ill check the plugs and then the coils, what should be the output of each coil?
Expert:  Lou P. master tech replied 11 months ago.

We don't have specs to ohm coils. What you can do is plug the plugs into the coils and lay them on the head and crank and see if they are all sparking.

Customer: replied 11 months ago.
I have tested both coils by removing the center wire on each distributor, putting a plug in the wire and setting that on the block. In each case the plug fires in rapid succession. Whats next?
Expert:  Lou P. master tech replied 11 months ago.

ok, unplug the mass air flow sensor,. its the big round sensor in the middle of the engine, it will have a round plug on it i believe, it will not be easy to unplug but it needs to be .

Customer: replied 11 months ago.
ok done
Expert:  Lou P. master tech replied 11 months ago.

OK see if the car will start. of course if all the plugs and coils are back in

Customer: replied 11 months ago.
it it hard but I starts for about 10 seconds, again only when I floor the gas pedal
Expert:  Lou P. master tech replied 11 months ago.

OK, try again with the injectors unplugged .

Expert:  Lou P. master tech replied 11 months ago.

and when it does start with the pedal floored does it run well or does it just start and die ? what does it do?

Expert:  Lou P. master tech replied 11 months ago.

WOULD you be up for a phone chat? I think we can clear some of this up faster for both of us. i will be available to chat after 5pm central time. i can send over the offer.

Customer: replied 11 months ago.
ok, tried starting it without injectors and it would not even come close to starting. When I started it with just the MAF sensor unplugged it start after cranking for 10-15 seconds, it builds up to it then starts all while I am flooring the pedal. When it starts it sputters for a few or last time 10 seconds. it does not and idle then die.
Customer: replied 11 months ago.
it does not start and idle then die. sorry
Expert:  Lou P. master tech replied 11 months ago.

OK , mass air plugged back in, injectors plugged back in, plugs and coils all installed, make sure fuel pump relay is in and also fuel pumps are connected (not sure if you ever disconnected.) then turn key on, wait 5 seconds, turn key off wait 5 seconds, turn key on wait 5 seconds turn key off wait 5 seconds, repeat about 10 times, then see if it starts without pressing the gas pedal.

Customer: replied 11 months ago.
Ok, I plugged everything back in and tried the on/off key sequence. it almost started but didn't. I then tried to start it by pressing the pedal down and it would not start. I repeated the key sequence again but this 2nd time it didn't come close to starting.
Sorry this is so much trouble. What should I do next?
Customer: replied 11 months ago.
Any thoughts?
Expert:  Lou P. master tech replied 11 months ago.

well, even though we have good pressure, i think the flow may be a issue, so far we concluded that fuel and spark are ok, so it must be a lack of fuel,. but first i want you to see about getting a noid light to plug into the injectors so we can verify the injectors are firing when cranking. you can buy or rent from a autozone.

Customer: replied 11 months ago.
Ok, I checked each injector harness plug and the light flashed at regular intervals on all eight.
Expert:  Lou P. master tech replied 11 months ago.

ok, what the hell is going on lol. we have spark, and fuel......... ok do you have a second person to help you?

Customer: replied 11 months ago.
Expert:  Lou P. master tech replied 11 months ago.

ok, have someone crank it while you plug the exhaust to see if you have air flow. it should make some decent pressure. use rags or towels.

Customer: replied 11 months ago.
I plugged it with a towel but couldn't tell if much so I covered each exhaust with my hand/plastic glove and felt airflow but not a ton.BTW, I would like to work through all possible ideas and testing through the day and if we need to do a call after 5:00pm Central time, I am ok with that, unless we fix it before.
Expert:  Lou P. master tech replied 11 months ago.

ok, i am just running out of ideas here. none of this adds up. we are missing something.

Customer: replied 11 months ago.
Could it have something to do with the Engine Management System? The Bosch LH/EZL Computerized Engine Control System and/or the Advanced electronic control units (ECU)
Expert:  Lou P. master tech replied 11 months ago.

yes BUT with the car cranking and injecting, it doesnt make sense. at this point it will have to be scanned with a scan tool to see what values the computer is seeing while its cranking. to me it sounds like a electrical or sensor issue. i dont think we can do anymore at this point without a scan tool.

Customer: replied 11 months ago.
my 94 doesn't is pre-OBDII. I have a X11/4 round port that there are scan tools for but I don't have one and I believer they are hard to find. I do haver a scan tool i built from some radio shack parts that can read the codes via blinking lights. have you ever heard of this type of a scan tool? see attached files.I did read the codes prior to starting and here are the results:Port 6 - 26 blinks = Upshift delay 1 to 2 (model 123.034) , 2 to 3 (all models)
Port 7 - 2 blinks = Heated Oxygen sensor inoperative
Port 8 - 6 blinks = Idle speed control inoperative
Port 17 - 8 blinks = Engine coolant temperature sensor, open/short
Port 19 - 3 blinks = Lambda control inoperative
Port 21 - 6 blinks = Idle speed control inoperative
Port 22 - 2 blinks = Heated Oxygen sensor inoperative
Port 23 - 15 blinks = Wide open throttle information defective
Port 30 - 2 blinks = Heated Oxygen sensor inoperative
Port 31 - 2 blinks = TN-signal (rpm) at LH-SFI control module (N3/1) defective
Expert:  Lou P. master tech replied 11 months ago.

yes sir, its what we used in the shop until the computer system came out. i like the coolant temp code ! that could be a issue, also i forgot a very vital piece of info, have you heard of the wiring harness issue? if you move your wiring harness does the insulation of the wires crack off??

Customer: replied 11 months ago.
Great, I want to make sure I captured all of the codes and blinks properly. I had good instructions how to build the scan tool but not on how to use it. After turning the ignition on so all the lights appear on the dash, I put the Red wire in the port 3 and black in port 1, then I take turns placing the yellow wire in all the other ports and recording the blinks. Is that correct?
Customer: replied 11 months ago.
Also, yes I am unfortunately aware of the wiring harness issue with Mercedes 1990 to 1998 harnesses. I do not yet have a content ASR issue so I have not replaced the harness (very expensive anyway) Could the harness cause these starting issues I am experiencing or is it more tied to the ASR randomly coming on?
Customer: replied 11 months ago.
BTW, I purchased and replaced the temperature sensor and both CSP sensors. I have also purchased a new Bosch Oxygen sensor but have not replace it yet.
Customer: replied 11 months ago.
Also, the last item i listed above was actually 11 blinks not 2 but the diagnostic was correct see below:Port 31 - 11 blinks = TN-signal (rpm) at LH-SFI control module (N3/1) defective
Customer: replied 11 months ago.
OK sorry for over loading you with all of that info. What is my next step???
Expert:  Lou P. master tech replied 11 months ago.

Ok yes overload haha. Next step is to check the wiring for cracking. Did you find any bare wires anywhere ?

Customer: replied 11 months ago.
It doesn't appear to be full of cracked or falling apart wire insulation
Expert:  Lou P. master tech replied 11 months ago.

Ok. Well that's a good sign. I'm out of ideas. Even though we have codes they don't mean nothing without seeing some actual values , codes are helpful in a sense but I'm not sure we can diagnose this here. At least I can't. If you wish we can stop now and you can have a shop look at it? Or I can opt out and see if another expert can help. But I am out of ideas at this point and don't want to guess at anything. I appreciate your Patience. Let me know how you wish to proceed.

Customer: replied 11 months ago.
i am unfortunately not in a position to spend a ton of money on a shop right now. I would really appreciate you sending me to another expert. One that you believe is he best and willing to go through this one step at a time again. Thank you again and I really appreciate your help!
Expert:  Lou P. master tech replied 11 months ago.

Ok I wish you the best. Good luck.

Expert:  Juan Crespo replied 11 months ago.

Hi there. Expert Lou P. is one of our best and, as such, a tough act to follow. He's basically touched on every possible cause for the existing condition. The only thing I can think of adding would be to check the injector pulse signal in case the LH-SFI has gone bunkers and is keeping the injectors open by constantly grounding them - other than that I just couldn't explain why the spark plugs are getting wet.

Would it be possible for you to rig an LED or get a Noid light (less than $20 at most auto parts stores) so we can check and see if the the ground signal to the injectors is constant or intermittent?

Customer: replied 11 months ago.
Hi Juan!I have a noid light to plug test kit. I checked each injector plug and the light flashes at regular intervals that seem to be matching when the distributor would be sending the spark to that plug. I did this on all eight of the injector plugs and they all responded the same. Is that the appropriate behavior?
Expert:  Juan Crespo replied 11 months ago.

That is the proper behavior indeed.

I'm grasping at straws now, but how many miles are on that engine? could we have a stretched timing chain causing compression issues?

Customer: replied 11 months ago.
I am the original owner I have put all 190,000 miles. It has been well maintained but i have seen a puff of smoke occasionally when I start the car but it doesn't really burn oil. It has always has great acceleration but I have has some idle issues off and on for 6 months. When this happened I was almost out of gas, I do mostly city driving. I was on a city street going 35 mph and all of a sudden it seemed like it ran out of gas. It lost power but kept running for about 200 yards then it died. I was 25 yards from the station and has a gas can so I filled it up and put it in the car but I couldn't get it started
Customer: replied 11 months ago.
Lou instructed me to empty the gas tank when it seemed like their was water in the gas. i pulled the plugs and cleaned them off but i didnt check to see if the plugs were wet again after cranking it. Should I do this.
Expert:  Juan Crespo replied 11 months ago.

It can very well be more than just one thing causing the issue, that's why I don't see any harm in pulling the plugs again, specially when I'm about to ask you to perform a compression test. If compression varies 10-15 % or more from cylinder to cylinder, we'll know we have a stretched timing chain.

Best Regards.

Expert:  Juan Crespo replied 11 months ago.

Oh, Oh... wife is giving me "the look". I got to put the laptop away and come to dinner. I'll try and check on you later tonight or tomorrow.

Best Regards.

Customer: replied 11 months ago.
Ok, I know that look. Thanks and speak with you tomorrow.
Expert:  Juan Crespo replied 11 months ago.

I ate like a good boy so I was allowed to check one last time. Talk to you tomorrow...

Customer: replied 11 months ago.
I did a compression test and all were at 120psi until I got to the last cylinder (#7) passenger side closest to the fire wall, it read as below 60psi. is that my issue?
Expert:  Juan Crespo replied 11 months ago.

I'm afraid so. Just to confirm, disconnect the fuel pressure regulator vacuum hose and connect a vacuum gauge. Have a helper crank the engine while you monitor the gauge; if you don't get at least 3.5-4 "Hg I'd say valve timing is off and it's time for a new timing chain set.

Best Regards.

Customer: replied 11 months ago.
I don't have a vacuum gauge so I will need to rent or buy one to complete the test. I am fairly handy and have attention to detail but is replacing the timing chain something I should attempt to do?
Expert:  Juan Crespo replied 11 months ago.

Timing chain replacement on a M119 is not something I would recommend doing unless you are an experienced tech and have all the necesary tools.

Best Regards.