The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-11-2018, 06:18 PM   #1
randywa
Registered User
 
Join Date: Nov 2012
Location: Republic, Mo.
Posts: 34
Question fuel pump quits on hot days

I may be overlooking something simple and obvious. The fuel pump on my 93 5.7 with auto has been quitting me, but only when on and off throttle a lot (hills and curves), the air temp is above 90, and running the a/c. It doesn't surge, stumble, or give any warning. It apparently doesn't even care how deep the ditch is or if the road has a shoulder to park on. It will always start after 30 minutes or so. Sometimes I can switch out the relay and it starts right away, but not always. Today I noticed it threw a blink code 15 - Engine coolant temp sensor error (low temp indicated). The code went away as soon as the motor started back up. I've pulled the bed and repaired the frame ground at the pump and cleaned all the grounds I can find. While the bed was off I fought thru a very fast idle problem, replace the knock sensor, tps, and coolant sensor. I've also chased more wire than a truck should have, just looking for bad spots. I've read all the threads I could find about fuel pumps and can't seem to figure it out. The people with the big butterfly nets are going to come take me away soon if this keeps up. Any and all help is greatly appreciated.
randywa is offline   Reply With Quote
Old 07-11-2018, 09:26 PM   #2
ChevyTech
Registered User
 
Join Date: May 2004
Location: Minnesota
Posts: 4,620
Re: fuel pump quits on hot days

Look at all the grounds at the front of the intake manifold.

The 1993 schematic shows the ground for the fuel pump terminates at the front of the intake manifold on G108 & G109.

The computer & sensor grounds share the same grounds on G108 & G109. One ground is by the thermostat and the other under an intake bolt / stud on the drivers side front of the intake.

If the coolant sensor loses its ground it will set a code 15, which will case the computer to command a faster idle speed.
__________________
For those of you that are wondering why you are not getting replies to your thread:
Did you give the model, year, engine, fuel system type, and transmission information?
If it is modified from what came stock from the factory, let us know that too.
ChevyTech is offline   Reply With Quote
Old 07-11-2018, 09:54 PM   #3
randywa
Registered User
 
Join Date: Nov 2012
Location: Republic, Mo.
Posts: 34
Re: fuel pump quits on hot days

I just looked at mine again. Instead of being split up all 4 wires are all on the stud by the sensor. Should I split them up or does it matter as long as they're clean and tight?
And come to think of it, when I was have idle problems, the TPS was showing short to ground so I changed it out. I'm beginning to think I better run the wiring harness again. Maybe a rub in there I missed before. Thanks for the reply.
randywa is offline   Reply With Quote
Old 07-11-2018, 10:31 PM   #4
ChevyTech
Registered User
 
Join Date: May 2004
Location: Minnesota
Posts: 4,620
Re: fuel pump quits on hot days

The grounds should be split up.

I do not like having any of the grounds connected at the thermostat housing. I have seen to many that have lost their connection to ground when at the thermostat. I always move them to a intake stud.
__________________
For those of you that are wondering why you are not getting replies to your thread:
Did you give the model, year, engine, fuel system type, and transmission information?
If it is modified from what came stock from the factory, let us know that too.
ChevyTech is offline   Reply With Quote
Old 07-19-2018, 07:57 PM   #5
Tom
driving is in my blood
 
Tom's Avatar
 
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,687
Re: fuel pump quits on hot days

Whats the fuel pressure when its running correctly?
__________________
-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle.
-98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes.
-02 Suburban 4x4: leveled front
-CBR600F4i, CBR600RR, CBR1000RR, and standup skis
DISCLAIMER: I cant spell for the life of me.
Tom is offline   Reply With Quote
Old 07-21-2018, 02:06 AM   #6
randywa
Registered User
 
Join Date: Nov 2012
Location: Republic, Mo.
Posts: 34
Re: fuel pump quits on hot days

Tom, sorry I couldn't get back to you quicker. My computer had a hard time digesting some lightning.
It would run between 12 and 12.5 lbs of pressure. I think I found the problem though. When I pulled the fuel pump the wires on the pump itself almost looked burned and the connectors were pretty much gone. I replaced the pump and drove it about 80 miles in 90-95 degree heat with no problems. The old truck acted almost happy. I hope that has taken care of it.
randywa is offline   Reply With Quote
Old 07-23-2018, 03:35 PM   #7
Tom
driving is in my blood
 
Tom's Avatar
 
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,687
Re: fuel pump quits on hot days

Excellent good luck
__________________
-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle.
-98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes.
-02 Suburban 4x4: leveled front
-CBR600F4i, CBR600RR, CBR1000RR, and standup skis
DISCLAIMER: I cant spell for the life of me.
Tom is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:56 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com