1997 Sierra 5.0 Starting Issue

[ColeTrains03]

Ok guys my uncle called me up from MN(i'm working in ATL) and asked for my opinion. He just had a new fuel pump installed like 2500 miles ago and the truck used to start fine. Well now it sometimes starts but then falls dead after a brief idle. Sometimes it doesn't start at all. He tested for fuel at the Shrader valve and it's got fuel and we confirmed spark. I don't know alot about the 5.0 engine so i'm not a whole lot of help but i was able to help him narrow down to a couple things. Either he's not getting enough fuel pressure or it's not getting spark at all times or a strong enough spark to start. Any idea's from you guys would be helpful ~Cole~

[ColeTrains03]

nobody?

[VRSCA1]

nobody?

 

When the concern happens he will need to verify proper fuel pressure at the rail,55 psi is the minimum fuel pressure generally required to pop off the fuel injectors on this system unless the newer CSFI unit has been changed over to the multec fuel injector design.

Will need to verify spark is present which is easily done with a tester.

Also check the fuel pump connector at the fuel pump module have seen overheated terminals that are spread and fatigued.This will cause intermittent fuel pump operation.Swap the fuel pump relay with lets say the horn relay in the U/H PDC center,this way a fuel pump relay can be ruled out.If it was the relay this will be confirmed with no horn operation intermittently,they use the same relay # in most cases if my memory serves me correctly.This is a quick way to narrow it down also if no diagnostic equipment is available.

Another angle would be what kind of fuel pump module was installed? Sometimes aftermarket fuel pumps will save money on repairs,but in the end you get burned anything other then a pump from GM parts supplier I steer clear of,spend the extra money on a delco,delphi gm supplied fuel pump module or you end up pullling the fuel tank twice.My money would be on a parts quality issue if an aftermarket fuel pump was used instead of a gm one or the fuel pump connector terminals were overlooked when the fuel pump was replaced intially.

[ColeTrains03]

I do believe he said the pump was aquired from O'Reileys so i'm guessing it's aftermarket. I will discuss this with him

[Graya25]

I have the same truck (1997 Sierra w/ 5.0) and I'm pretty sure it's a problem with the fuel pump not building enough pressure. In the winter the truck was hard to start in the morning, so I've replaced the fuel filter, spark plugs and distributor cap, and it still is difficult to start on a cold morning. Those being replaced, the only logical part that could be a problem would be the fuel pump, which I haven't taken a look at since I really do not want to drop a 34 gallon tank on my daily driver.

Take another look at the fuel pump and make sure it builds enough pressure.

[rodram]

strongly suspect the fuel pump ... as mentioned above there is a lower bound limit for the fuel pressure where the vortec poppet valves will not function ... some say the lower bound is 55-58 psi ... GM specs on these pumps is 61 to 66 psi...

 

get the fuel pressure checked ... even a relatively new pump can fail ... as someone said... get a ACDelco or a Delphi brand for best reliability

 

if the fuel pressure is OK then get the ignition module checked....

[ColeTrains03]

well i guess he got it started yesterday and it ran good. Then when he shut it off and went to start it this morning it wouldn't start. He said he checked the oil and it smells alot like gas. Is there a fuel pressure regulator located in an easy spot to check? the reason i ask is i had this issue with my '96 Z28 when the regulator went out on it. Wouldn't start and then when it did and i tried to start it again it wouldn't. Just a thought too

[rodram]

well i guess he got it started yesterday and it ran good. Then when he shut it off and went to start it this morning it wouldn't start. He said he checked the oil and it smells alot like gas. Is there a fuel pressure regulator located in an easy spot to check? the reason i ask is i had this issue with my '96 Z28 when the regulator went out on it. Wouldn't start and then when it did and i tried to start it again it wouldn't. Just a thought too

 

Hi... still sounds like a poor fuel pump... when I had trouble starting mine last year, my mechanic also told me I had gas in my oil when I got the fuel pump changed... he also recommended getting the oil changed .....

 

so I would still get the fuel pressure checked and the fuel filter inspected (or changed) and now i would add getting an oil change to the list

[ColeTrains03]

Yeah i told him pressure check is needed so he's gonna get one later this week. He put a new fuel filter on when trying to figure out this issue but the one he pulled turned out to be fine. He still has the new one. I just hope he gets it fixed soon

[ColeTrains03]

Could it be a leaky injectors? I don't know alot about the 5.0 but if he's showing Fuel pressure drop at the shrader wouldn't it point to either injectors OR a pump?

[ColeTrains03]

*UPDATE* Fuel pressure checked and it was 55psi with key on. When he started it(which it did easily) it was at 61-62 psi and when he gave it gas it went to 65 psi. Any other thoughts?

[Badass69]

The fuel pressure regulator is pretty notorious for failing on these trucks. As are the poppet valves on the factories CPI which is why the Multitech II injector upgrade exists. Your fuel pressure looks fine so it's probably a good chance it is something else.

[Tres_Chevys]

i have a 97 chevy with the 305 and 8 years ago when i bought it if i would have known i was going to have half the problems ive had i would have kept going when i saw it on the lot. i share your uncles problem with hard starting, after 3 pumps in a 6 month span along with all new injectors, both filters (tank, frame rail) and running premium as an almost last ditch effort, i still have not found the problem. i plan on changing the regulator this weekend, weather permitting, and ill update. please update me as well. also if you change the pump, the factory ground location is crappy, people suggest cleaning the ground connection, i suggest moving it all together.

[rodram]

i have a 97 chevy with the 305 and 8 years ago when i bought it if i would have known i was going to have half the problems ive had i would have kept going when i saw it on the lot. i share your uncles problem with hard starting, after 3 pumps in a 6 month span along with all new injectors, both filters (tank, frame rail) and running premium as an almost last ditch effort, i still have not found the problem. i plan on changing the regulator this weekend, weather permitting, and ill update. please update me as well. also if you change the pump, the factory ground location is crappy, people suggest cleaning the ground connection, i suggest moving it all together.

 

... replace the fuel pump 3 times in 6 months ....? ... this is why you have to get a ACDelco from the dealer or a Delphi (who makes the ACDelco) from a good parts house ... there are too many cheap brands and counterfeit pumps out there ... if you get the proper pump then you will likely not have any future fuel pump problems ... yes, and replace the sock and replace the wiring harness as well when you put in a new pump

[rodram]

*UPDATE* Fuel pressure checked and it was 55psi with key on. When he started it(which it did easily) it was at 61-62 psi and when he gave it gas it went to 65 psi. Any other thoughts?

 

if you are confident in the fuel pressure, then I would next check the ignition module.... these little things can cause intermittant stall and non-start issues ... they can work fine and then not work ....