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Tool Hut
Tool Hut, ASE Certified Technician
Category: Chevy
Satisfied Customers: 522
Experience:  Owner of a mobile diagnostics company assisting auto technicians with difficult vehicles
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This chevy pickup we put a fuel pump in it a year ago and it

Customer Question

This chevy pickup we put a fuel pump in it a year ago and it went bad so we put another in it 2 weeks ago and it run well and it stated getting colder and it would not start. Checked fuel pump and it has 55 psi so we went a different direction and put spark plugs in it plus a ignition control module and now it runs for 40 seconds and dies but it starts right back up and dies again.
Any suggestions
Thanks Eddie
Submitted: 1 year ago.
Category: Chevy
Expert:  Roy replied 1 year ago.

good morning my name is ***** ***** I will assist

when the truck stalls after 40 seconds, was the fuel pressure still 50 lb

Roy

Customer: replied 1 year ago.
it holds there for 20 minutes an slowly drops back 4 pds. is all.
Expert:  Roy replied 1 year ago.

ok, then it does not sound like a fuel issue.

did you have the ignition module checked??? you can remove it and have it tested at a parts store for free.

Roy

Customer: replied 1 year ago.
You mean the new one I put on it?
Expert:  Roy replied 1 year ago.

yes, there has been times that we get bad new parts. just trying to be sure that it is not failing when it heats up

Roy

Customer: replied 1 year ago.
Ok we went and got another new one and they tested them both and said they checked ok.
Expert:  Roy replied 1 year ago.

do you have any way to monitor data with a scan tool. Looking to see if you loose spark when it stalls.

did you clean the throttle body real well??? you may have a crank sensor acting up

Roy

Customer: replied 1 year ago.
Back with you Roy this think is not getting fuel I know it has pressure but not enough volume but when you turn the key to off it has a lot of volume. Any suggestions, we are now on our 3rd.. fuel pump.
Expert:  Roy replied 1 year ago.

what is the actual pressure???

Roy

Customer: replied 1 year ago.
55 psi
Expert:  Roy replied 1 year ago.

thats not bad. I doubt you have 3 bad pumps. I would drop the tank and examine the internal part of the tank for any damage. if you have no volume, it originates at the tank

Roy

Customer: replied 1 year ago.
when you turn key on the volume is past a dribble but when you turn key off pump will run for 5 seconds with full volume of gas
Expert:  Roy replied 1 year ago.

ok, you need to monitor the voltage when this is happening. it sounds like you are losing voltage with key on.

Roy

Customer: replied 1 year ago.
Ok Roy we put a new plug on it and checking the voltage with the key on not cranking it is 12.0 and when cranking it goes to 11.5 but I notice the fuel gauge still full all the time.
Expert:  Roy replied 1 year ago.

does it stay constant while running>>> we are looking for the voltage when it has the problem

Roy

Customer: replied 1 year ago.
No when we are cranking it, it stays at 11.5 but no fuel to rail. I can spray clean carb. in the throttle body and it runs until I quit spraying the clean a carb.
Expert:  Roy replied 1 year ago.

ok, thanks.

that is telling me the pump is not working. this whole thing does not make sense.

did you replace just the pump or the whole module???

Roy

Customer: replied 1 year ago.
When I replace fuel pump I usually change the whole module assembly.
Expert:  Roy replied 1 year ago.

I am wondering if the is a problem right at the module between the sonnector and pump.

usually>> ok, but did you do it this time??

Roy

Customer: replied 1 year ago.
I still have the old pump I could try putting it back in since we changed the connector. I am total lost on this thing...LOL
Expert:  Roy replied 1 year ago.

I wish I was there to help you. check the resistance from the top connector to the fuel pump itself

Roy

Expert:  Roy replied 1 year ago.

please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 1 year ago.
How can we test the injectors on this unit I am getting fuel up to that now.
Customer: replied 1 year ago.
I did test the injectors with a noid light and they are all showing voltage.
Expert:  Roy replied 1 year ago.

ok, the light lights up but does it flash when cranking the motor. that will tell if the pcm is firing the injectors

Roy

Customer: replied 1 year ago.
it flashes while cranking
Expert:  Roy replied 1 year ago.

ok, then the computer is working. you say there is fuel there. have you checked the pressure???

Roy

Customer: replied 1 year ago.
there is fuel only at the line at the injector harness and the pressure is 55 psi. Do you think that injector spider is bad, just a thought.
Expert:  Roy replied 1 year ago.

fuel pressure is good. do you have good spark??

Roy

Customer: replied 1 year ago.
we have goo spark, all new spark plugs too with a 60 gap
Expert:  Roy replied 1 year ago.

pull a spark plug and see if it is fouled with fuel. do a compression test on that cylinder as well.

Roy

Customer: replied 1 year ago.
none of them are fuel fouled, they are all dry.
Expert:  Roy replied 1 year ago.

and the compression???

Roy

Customer: replied 1 year ago.
Just got done checking compression and it runs from 115 to 125 psi per cylinder. There is still not fuel showing on spark plugs either. I have never had this much problem with a vehicle. LOL
Expert:  Roy replied 1 year ago.

it is possible you have a bad spider unit. all the other checks are good.

Roy

Customer: replied 1 year ago.
Ok we did put a remanufactured spider in this also.
Expert:  Roy replied 1 year ago.

ok, keep me updated

please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 1 year ago.
The injectors did not fix it either Roy.
Expert:  Roy replied 1 year ago.

if the noid light is blinking as you say cranking, the crank sensor is working and fuel should be delivered into the cylinders since you have the pressure.

I am out of ideas here. I will open this up to the other guys to see if anyone has any better ideas

Roy

Expert:  Tool Hut replied 1 year ago.

Hi, My Name is ***** ***** for posting your question to just answer. I am a independent contractor for just answer, and ASE Certified Master Auto Technician with 20 years experience. I am confident we can resolve your problem together.Please remember I don't know your skill level. I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies to get to a satisfactory resolution.There will probably be some equipment needed for a proper diagnosis. If you are not comfortable with this or do not have any test equipment please let me know ASAP. I also try to give all of the information you may need expecting a positive rating. I am not compensated for my time until you leave a positive rating.

HAve you checked your grounds at the pump connector?

It should have 2 grounds. They are very common for a ground wire breaking. Try running a separate ground wire to the black and black with a white stripe wires. They should be kitty corner form each other.

Customer: replied 1 year ago.
I did have a ground problem so we run a ground from the front of the pickup back to the one ground and even tried trying both grounds together, plus we took a battery back there and tried that too. Thanks for coming in and trying to help us with this problem Samuel, I appreciate all the help we can get here.
Expert:  Tool Hut replied 1 year ago.

When you turn the key on what is your voltage at grey wire and then after it starts do you lose voltage?

Expert:  Tool Hut replied 1 year ago.

The fuel pump relay runs the pump for a few seconds and then the oil pressure switch provides power. Check for power at oil pressure switch. Try jumping 2 wires on outside and see if it runs

Customer: replied 1 year ago.
Ok we will try that, I did notice while cranking it on the oil pressure gauge it showed 40 psi.
Expert:  Tool Hut replied 1 year ago.

It may not be driving the fuel pump though. Very common problem on these. You should have power at 1 wire with key on and engine off. Check that first. There are 3 terminals. Center is gauge and outside 2 run fuel pump

Expert:  Tool Hut replied 1 year ago.

orange and grey wires run pump. Orange is power

Customer: replied 1 year ago.
Ok when the key is off the voltage shows 11.55 across the 2 wires on the oil pressure sender, when turn the key on it shows 11.27