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John, ASE Master Technician
Category: Car
Satisfied Customers: 574
Experience:  ASE Certified Master Technician, ASE Certified Service Consultant, 22 years professional experience
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1996 mazda 626: wont start mornings (cold..starts fine..Fuel filter

Customer Question

1996 mazda 626 won't start mornings (cold - 4- deg) but starts fine afternoons (warm - 60 deg) , Fuel filter has been replaced.
Submitted: 5 years ago.
Category: Car
Expert:  lnsmman58 replied 5 years ago.

Hello there I'm Scott,

Does it turn over ok when its cold or does she turn slow? Describe how it acts when cold and lets try to figure this out. Cold weather can bring out problems that warm weather doesn't affect. Fill me in here. Thanks.



Customer: replied 5 years ago.
Turns over just fine - high speed. Just doesn't fire at all. Pops right off when warm. Often times though, it won't start on the first try (historically speaking) - it would go for 9-10 cranks and then I let off the key and then a second later it would start on the first crank.
Expert:  lnsmman58 replied 5 years ago.
Thank you for that info. How many miles is on this car? What kind of service have you performed over the years, beside just oil and such?
Customer: replied 5 years ago.
170k. Bought it from a college kid when gas prices were so high cause I couldn't afford to drive my truck to work. I farm and work over an hour away. Gets 35mpg :) Since I've had it I've just stayed on top of min. maint. - tires, OFL, fluids and such. Also ran a tank of system cleaner/drier first before changing fuel filter. Filters checked and okay. Had to disconnect a lot of the electrical gadget connections to change the filter - have pulled and reconnected all to make sure they were making good contact. Purrs like a kitten when running (yesterday). Actually like a really big kitten - it does have an exhaust leak.
Expert:  lnsmman58 replied 5 years ago.

Please be sure you are 100% satified with my answer before you hit accept!


Hmmmm, Well you are getting up there on miles and what you might be experiencing is a compression drop, which can cause a hard starting problem. It could be nothing other then that, but ya might try cleaning your mass flow sensor(you can get a cleaner at your parts store) and see what happens with that, while you are at your parts store you could have them run a test for codes and see if there is any stored in the computer pointing at something. Then if nothing comes up and if nothing I'd run a compression test to see where you are on compression. From what I've found that is a high compression engine and runs at about 195# XXXXX if it is considerably lower that is probably whats making it harder to start in the cold. I hope this info helps you out.



Customer: replied 5 years ago.
Has not thrown any codes... I took it in checked before and after the fuel filter change - yesterday. Other than that, does not burn any oil, is strong on accelleration and load (even yesterday when it warmed up outside and it started fine). That, combined with the sudden onset of the problem leads me to believe compression is okay. Am I off-base on this? Also, some web forums indicate there might be a cold air temp sensor somewhere, which seems to make sense - but I don't have any manuals and I'm hell and gone from the closest place I might be able to get one - so even if there is one, I don't know where it is and how to field check it.
Expert:  lnsmman58 replied 5 years ago.

Well that it is very posible, but ya I don't know enough about this system to give you acurate infromation here. I'm going to opt out and see if I can find you a mazda expert ok. I wish ya lots of luck here. Hopefully an expert will be right with (if i can find one online) Thanks for using JA!



Customer: replied 5 years ago.
okay, thanks anyway.
Expert:  lnsmman58 replied 5 years ago.
I've sent it over to another tech, hopefully he will read his message and get right with you. This is out of my control though, I wish I could have been more help. I took a look at the wiring diagram of the vehicle and didn't see a cold start sensor, thats why I'm not sure where to go with this. Sometimes diagrams are kind of generic and don't show everything. If you don't hear right away I'd post it over in that mazda forum and see if you can't get an answer there.
Customer: replied 5 years ago.
Appreciate it... if I'm going to make a trip to town for parts and such I'd like to have a clue what the @#@ I'm chasing!
Expert:  lnsmman58 replied 5 years ago.
lol, I totally agree with you there! Wish I could have helped!
Customer: replied 5 years ago.
Have a good one...
Expert:  John replied 5 years ago.
Hi Rob

Scott asked me to share my thoughts on this problem. I think from reading your post I think you have some kind of fuel delivery problem. Low fuel pressure, low flow volume, residual fuel pressure loss (leaking injector or pressure bleeding down at pump, fuel leak) something like that.

I you can get a fuel pressure gauge I think we can pin it down. Some auto parts stores have loaner tool programs and hopefully will have a fuel pressure gauge that you can use.

Here is what you will do:

Install the fuel pressure gauge in the hose between the fuel filter and the engine.

Run the engine. Fuel Pressure should be 36-47 psi.
If it is too low then you may need a fuel pump. The pump may not be delivering enough fuel at key on to make the car start easily cold.

Turn the engine off & watch the fuel pressure gauge. After 5 minutes of sitting with the engine off the fuel pressure should still be above 21 psi. If it is not then you are loosing pressure somewhere so the pump has to work harder to build up pressure before the engine will start while you are cranking.

If the fuel pressure drops below 21 psi, repeat the test (run engine & shut off) only this time when it is shut off immediately clamp off the fuel line between the gauge connection and the filter (so no fuel can flow back to the filter). and after 5 min ck pressure. If the pressure is now ok then the fuel pump check valve has failed. If it drops again then do the same test again except this time clamp off the hose between the gauge connection and the engine (so no fuel can flow to the engine). If this stops it from bleeding down then the fuel injectors are leaking.

The fuel pump check valve is an integral part of the fuel pump so the only way to replace the check valve is to replace the whole pump. If the injectors are leaking then you need new injectors.

Let me know how all this turns out for you.

Customer: replied 5 years ago.
Okay... but right now it's cold and it won't start. What you suggest makes sense, but if I cant start it, what can I do in the mean time to pre-check?
Expert:  John replied 5 years ago.

Sorry. So much info I forgot it wanst starting now - oops.


You can still test fuel pressure bleed own just by cranking the engine with the key. Or you can use a jumper wire (read paper clip) to jump the test terminals under the hood to run the pump. See the diagram below:




This connector is near the battery.


Let me know what you find or if you have any other questions.



Customer: replied 5 years ago.
Okay.... will do. Do have one other issue confusing me though... This thing has (what appears to be) a vacuum-operated pressure relief valve mounted at the end of the injector manifold that goes to (again, what appears to be) a return fuel line back to the tank. Won't that screw with the fuel pressure drop readings you want me to get? (Hope I'm not testing your patience)
Expert:  John replied 5 years ago.
No problem. Feel free to ask questions.
I think you are talking about the fuel pressure regulator.
The small hose going to it is a vacuum hose used to control fuel pressure based on engine vacuum. You don't need to do anything with it for these tests. However, just to check it you can pull off the small vacuum line and look inside it. It should be dry, if it is wet with fuel that means the regulator has failed. The larger hose from that regulator is the fuel return line. You can clamp that off also during testing to see if anything changes.

If you get the engine running with the gauge connected you can test the regulator by again pulling off the small vacuum line and watching the gauge. With the engine running & the vac line removed you should see the pressure increase a few pounds on the gauge.

Customer: replied 5 years ago.

Okay... will do. Ya know if this was an IH or John Deere I'd have the @@#$ thing fixed by now...


I'll get back to you after finding a fuel pressure gauge checking some of these things out...

Expert:  John replied 5 years ago.
Tell me about it!
Customer: replied 5 years ago.

Okay. So I pulled the vacuum line off the fuel regulator. too small to see inside but it smelled like fuel. Ran a qtip in it and that smelled like fuel, but not noticably wet. Put the vacuum line back on and the car started right up.


Just checking to see if that's significant at all. I still have to do the fuel gauge stuff - I just started with the easy check that I didn't have a 2 hour round trip for.

Expert:  John replied 5 years ago.
You might have a problem with the regulator. Try checking it again after the engine has run for a bit. It's possible the regulator is causing your problems or is related to them. I would still do the gauge tests but if disconnecting the regulator works for you until then it wont hurt anything. Make sure to reconnect it once the engine is running.

Customer: replied 5 years ago.
Went to town to 3 places and no one had a loaner fuel gauge. One didn't have any at all, the other 2 only had ones that hooked up to shrader ports on fuel manifolds (mine doesn't have one). NAPA was closed - might be able to find one there during the week. I'll be back...
Expert:  John replied 5 years ago.
Ok. Let me know.
Customer: replied 5 years ago.


Haven't had time to pursue your suggestions. I don't have a garage I can work in and I leave for work at 6:15 and don't get home til 7 or 8 pm. Dark and cold before and after work. Also makes for a tired boy.


I'll get back after it this weekend.

Customer: replied 5 years ago.

Hi John,


Sorry for the delay. 2 blizzards, the holidays, and several other distractions later, here's what I figured out...


Checked out the fuel system - pressures, check valve, everything okay. I was referred to a guy by someone I work with and he said to replace the distributor. I did. It works.


Thanks anyway... and sorry for the delay.

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