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Gary
Gary, GM Technician
Category: GMC
Satisfied Customers: 841
Experience:  Senior Technician
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1999 GMC Suburban stalls while driving, restarts and runs fine

Customer Question

1999 GMC Suburban stalls while driving, restarts and runs fine for a brief period of time then repeats.
Submitted: 1 year ago.
Category: GMC
Expert:  Gary replied 1 year ago.
Welcome! My name is ***** ***** I will do my best to assist you with this problem.
I am sorry for the long wait
will it stall even when your foots on the gas pedal driving at speed ?
or only with your foot off the gas pedal ?
does the check engine light come on ?
do you know if there are any codes set in the computer ?
has anything been done yet to correct this problem yet ?
what size engine is in this ?
Customer: replied 1 year ago.
Hi, Gary. Thanks for the help. Answers below:1) Will it stall even when your foots on the gas pedal driving at speed ?
or only with your foot off the gas pedal ? Stalls either way. Idle or at speed. Stalls foot on the gas or off and idling.
2) Does the check engine light come on ? Nothing lights on the dash.
3) Do you know if there are any codes set in the computer ? Fault codes are clean. Nothing stored.
4) Has anything been done yet to correct this problem yet ? No, not for this go 'round. I had to have ti towed in Feb and I replaced the fuel pump and filter (600 miles ago). Used a Delphi pump. Tank was spotless inside. Looked new. Required I update the wiring pigtail to install the pump, which I did. I replaced the pressure regulator when repairing an antifreeze leak on the intake manifold but that was 50K miles ago. Right now, I don't know if it's electrical or fuel related.
5) What size engine is in this ? 5.7L
Expert:  Gary replied 1 year ago.
how often will it do this ?
Customer: replied 1 year ago.
Every 30 seconds to maybe 5 minutes. It failed Saturday. I limped home about 6-7 miles. I had 5 stalls in that period of time.
Customer: replied 1 year ago.
I parked it Saturday and didn't have time to pull codes until this morning. It's been sitting untouched until today.
Expert:  Gary replied 1 year ago.
can you see what the fuel pressure is when its acting up ?
Customer: replied 1 year ago.
Is there a Schrader valve on the fuel rail? I read there is not. Need to go rent a pressure gauge.
Expert:  Gary replied 1 year ago.
there is a test port on the fuel line next the distributor drivers side rear of the engine
we need the fuel pressure tested key ON engine OFF and also note if the pressure holds or drops to 0 within a second
then what the pressure is when its running bad
Customer: replied 1 year ago.
Got a tester. Once installed, I bled the line using the pop off valve. I then turned the ignition on for 10 seconds, turned ignition off and back on for 10 seconds 4-5 times. Pressure was 58psi. It dropped to 53psi over the course of about 4 minutes. It stayed at 53psi.I started over and got the same results three times.It's currently idling in the driveway but hasn't stalled yet. I'll give it awhile and I'll report back.
Expert:  Gary replied 1 year ago.
let me know what it reads when it acts up
Customer: replied 1 year ago.
Idled an hour in the driveway. Nothing. Still running. Pressure holding steady at 52psi.I've owned this truck since new and never had an issue like this other than the one fuel pump failure this past February. Saturday I drove it about 20 miles. Parked it for lunch, came out and it started right up. Drove it 1.5 miles and it quit in the middle of the street while going 35-40mph. Coasted into a gas station. Hard to start. Had to let it sit 2-3 minutes. Once started, in died in about 30 seconds. It then started right back up. Drove it about three miles and it quit in a driveway. Started right back up. Drove it 1/2 mile and it quit in the middle of street going 25mph. Coasted to the side of the road. Hard to start. Drove it about three miles home. Stalled at the top of my driveway. Started right back up and I parked it. I haven't driven it since.The pressure gauge is hooked up right now so I can't drive it. No idea how to troubleshoot a problem that won't reoccur without any fault codes to go by.
Expert:  Gary replied 1 year ago.
that is the hard part about intermittent issues
the only one problem i see right now is that fuel pressure should be 60 to 66 PSI key ON engine off
can you see if the fuel filter is plugged up or restricted ?
Customer: replied 1 year ago.
I replaced it with the pump. How do I test it? Do I rig something to bypass it? Blow air through it?Gauge could have a little variance but it shouldn't be 10+psi off.
Expert:  Gary replied 1 year ago.
can connect the fuel pressure gauge to the fuel feed line from the pump into the fuel filter and do the key ON engine OFF and if its still low the pump has a problem
replace the fuel filter to be sure thats not it
but with it being intermittent like this im not 100 % sure the fuel pump will correct this issue
Customer: replied 1 year ago.
Okay, the kit has the adapter that screws into the inbound side of the fuel filter. I installed it but the adapter must be defective as it registered zero pressure. Further, it released no fuel when i pressed the pop off valve. The truck started and ran and I had to release the pressure to remove the adapter from the fuel filter.I did notice that there was a lot of pressure in the line when I pressed the Shrader valve to remove the filter. I released the pressure and then it would pressure up again. I had to release the pressure several times. I also released the gas cap pressure at the tank. Having done that, the filter was still under quite a bit of pressure when I removed it. I could blow air through the filter easily, as in no resistance.I have a set of factory service manuals for this truck. I didn't see where it listed the fuel pressure any where. Beore contacting you, I saw some forums that said pressure between 50-55psi when running is normal on this truck. You're the expert. I'll replace the pump again if it's suppose to be 60-66psi. Not a fun job, as you know.I'll have to find another pressure gauge tomorrow with an adapter that works and then advise what I find..
Expert:  Gary replied 1 year ago.
Key On Engine Off 60-66 psi
im just unsure if this will 100 % correct this problem
but thats what the fuel pressure should be
Customer: replied 1 year ago.
Sorry for the delay. Had a couple challenges. First, dead heading the pump was a challenge. Finding a M16 x 1.5mm bolt, plug or whatever proved a challenge. Found a Subaru oil drain plug that fits (pt####-##-####for the next guy reading this). Second, I used the GM TBI adapter at the fuel filter to pull a pressure reading. It's kind of a banjo fitting. The pressure gauge didn't get a reading from that fitting when I tried it previously inline with the engine running. With the pump dead headed, still no reading.I rented a second pressure tester thinking the first was defective. Same result. Both pressure testers will read at the fuel rail when everything is hooked up but not at the filter with lined forward of the filter open. Is there a safety feature that senses the fuel is not going through all the lines and back to the tank and thus shuts the pump down as if the vehicle was in a collision and had broken fuel line?I spoke to a Delphi engineer to get some spec on the pump itself. He confirmed the rail pressure should be 60psi max with the key on and engine off. Engine running it should be 54-55psi. He commented I'm a little low. With the pump dead headed, pressure should read 65-130psi measured at the filter. He went on to say the electrical connections at the pump or relay can lower the pressure. He would not come right out and say it but he indicated there have been problems with the factory's pigtail wiring kit and the crimp on connectors included in the kit. Ideally, the pigtail should be soldered in.........but the instructions don't say that. The two main culprits he called out were the electrical connections on the pigtail needed to support the 9.6 amp draw needed and the fuel pressure regulator. To test, the first place to start was to dead head the pump as you suggested. Back to how to get that reading to work. I'm stumped getting zero pressure and no fuel flowing through the gauge pop off valve and hose. Yet there is pressure when the gauge is removed as it sprays some fuel. The likelihood of having two bad gauges or fitting is really low.Your thoughts?
Expert:  Gary replied 1 year ago.
yes there were many problems with the fuel pumps and or the connectors at the fuel pump module
you should be able to unscrew the fuel line going into the fuel filter from the tank and attach a fuel pressure gauge with a 3/8 rubber hose and a few hose clamps to be able to test key ON engine OFF fuel pressure
Customer: replied 1 year ago.
I rigged up a test line with rubber hose, as you suggest. Used a brass T with a Schrader on it. I put one 3/8" rubber hose over the metal fuel line w/o the filter. The other end of the T is has a second rubber hose blocked with a drill bit.Net results are the same. I can hear the pump run. I remove the gauge and get a little fuel. If I press the Schrader, there's not much pressure there. The metal tube is short now so there shouldn't be much after removing the gauge.Next test, I left the key on and can hear the pump cycle up. I pressed the Schrader I mounted in front of the inbound side of the filter with a small screwdriver. A little fuel sprayed and it stopped. Remember, the key is on and the pump cycled up. I press this Schrader and I should get A LOT of fuel if that line has 65-130psi in it like Delphi says it should. And it should replenish since the pump is on.1) Does this truck have such a safety system to shutdown the fuel pump? That might explain why most forum posts suggest crimping the return line vs dead heading the pump.
2) If it does have such a system, how do I bypass it so I can get a dead head reading?
3) If no such system, why am I getting virtually no pressure or flow at the filter with the key on?
Customer: replied 1 year ago.
Forgot to add I put everything back together and I get 58psi at the rail again.
Expert:  Gary replied 1 year ago.
no there is no shut off for the fuel pump
so not at the rail key ON engine OFF it has 58 and holds ?
Customer: replied 1 year ago.
Not at the rail with key ON and engine OFF gets no reading on the gauge. Won't even spray fuel with Schrader held open with a screwdriver.
Expert:  Gary replied 1 year ago.
will it run ?
Customer: replied 1 year ago.
Yes. When I put the fuel line back together it starts right up and runs fine. Put the gauge on the rail and I have a consistent 52psi when running.
Expert:  Gary replied 1 year ago.
see if any other experts have any ideas
hang on another expert will reply back to you
Expert:  Gary replied 1 year ago.
Does it slow stall like running out of fuel, or quick stall like turning the key off?
Sounds like a relay (EFI, Ignition etc) dropping out, poor contact in the fusebox.
Customer: replied 1 year ago.
It quick stalls. I initially thought ignition but with no fault codes and the fact the pump was just replaced, I moved to fuel first.
Expert:  Gary replied 1 year ago.
Stalling instantly is not fuel pressure related in your case.
I would tighten up all the "EFI" relay contacts to start with.
Gary
Customer: replied 1 year ago.
I'll tighten the EFI relay contacts. I'll have to look in the book to determine which relay it is unless it's labelled in the box.I have the tank back out right now. The fact my new pump pressure is a couple pounds low concerns me. To that end, I decided to solder the pigtail wires to eliminate that as a possibility both now and in the future. Anything else I need to check while I have the tank out of the truck? Is there a dead head quick connect fitting I can put on the return line to allow me to test the pump at the rail?
Expert:  Gary replied 1 year ago.
Hi there,
I don't think deadheading the pump is necessary if the car performs well.
Deadheading the pump will show what the pump is cable of, and may also show weaknesses elsewhere in the system. The regulator sets the pressure and dumps the excess via the return line.
You have an intermittent stall condition.
Is your pressure regulator vacuum referenced to the inlet manifold?
If it is I would check that there is no fuel in the vacuum hose, replace the regulator if it is wet with fuel.
I would measure the voltage at the pump, while the pump is running.
I had a customers car a few years ago that would stall after 15-20 mins of driving, stop and wait, would start again etc.
Eventually I could stall the engine just by moving the efi relay in the fusebox, tightened the females, problem solved. Customer had been to 4 different mechanics.
Hope this helps.
Gary
Customer: replied 1 year ago.
Tank is back in. Pressure is the same, which I expected. I'll tighten the relay, as you suggest, tomorrow. I also ordered a new Delphi pressure regulator. The big box stores only have the off brands. Normally they are fine. I want the OEM since we're chasing a problem that only happened one day. Granted, it happened 6-7 times that day.
Expert:  Gary replied 1 year ago.
If you are really keen, I would test the ohms reading of the relay contact when it is turned on.
To do this, hook your multimeter across 30 & 87 while on ohms scale, should read infinite ohms open circuit.
Then apply 12v + to 85 and ground to 86. Meter should read zero ohms.
Gary
Customer: replied 1 year ago.
I received the fuel pressure regulator yesterday. Quite a process to get. I removed the old regulator today and I believe have the incorrect part. They are quite different. Was there a design change to omit the vacuum port?I tried to attach pics but the Just Answer website won't let me do it. Here they are on Flickr.https:[email protected]/a3WV8m
Customer: replied 1 year ago.
Cross reference says it's correct. I removed a Borg Warner 23043. The Delphi cross reference tool says it's a FP10075, which is what I have.
Expert:  Gary replied 1 year ago.
Hi again,
You can't use that one, as you say completely different.
I wouldn't believe the cross reference.
Your original is manifold vacuum referenced, and the engine has varying fuel pressure according to load.
The other type would be fixed fuel pressure, which is meant for a different model with different PCM programming.
I would set up a pressure gauge in drivers view for further testing.
Could still be an electrical dropout though, did you find anything in the fusebox/relays etc?
Gary
Customer: replied 1 year ago.
I got a NAPA Echlin regulator and installed it yesterday. 58psi with engine off and key on. I get 51 psi with engine running. Basically, that changed nothing. I haven't found anything electrical either.I haven't been driving the truck but no issue other than that one day. I'm stumped finding nothing anywhere.
Expert:  Gary replied 1 year ago.
Sorry to hear you haven't found your problem.
But if it hasn't happened since, maybe you fixed it when you pulled some relays in and out etc.
Could have been a poor connection somewhere and you fixed it without even being aware of it.
Still sounds electrical to me.
Gary