truck failed to start - low fuel pressure?

[Chris253]

my truck failed to start about a week ago at about 4am and also refused to start again at about 4pm. while the engine was cranking it gave a chug and a backfire, so i thought maybe the pump was on its way out, just not completely yet. and then a couple of days later it started as if nothing happened. checked fuel pressure at idle in park is 57psi, when revved it goes up slightly and drops down to about 55psi. shut off for a few minutes it will sit about 64psi and slowly drop to about 61psi. the pump was replaced about 4 years ago with a delphi unit but i havent touched the injectors or anything else. do these numbers seem low? could it be injectors or should i look elsewhere? truck is a 97 k1500, thanks in advance

 

[Macs Garage]

Check your fuel filter? Probably not it, but should be replaced every year on these trucks.

 

[Macs Garage]

Check the fuel pump relay. I had a similar problem once. Wouldn't start for me, took it to the stealership and it started every time for them. They still replaced the fuel pump. Happened again and they replaced it again under warranty. Happened again and I gave the fuel pump relay a whack and it started right up. Replaced the relay and keep a spare in the glove box. Probably never needed a fuel pump.

 

[Chris253]

Check your fuel filter? Probably not it, but should be replaced every year on these trucks.

sorry, forgot to mention that was replaced a year before the pump went bad and then replaced again with the new pump

 

[Chris253]

Check the fuel pump relay. I had a similar problem once. Wouldn't start for me, took it to the stealership and it started every time for them. They still replaced the fuel pump. Happened again and they replaced it again under warranty. Happened again and I gave the fuel pump relay a whack and it started right up. Replaced the relay and keep a spare in the glove box. Probably never needed a fuel pump.

ill check that out. thank you

 

[stutaeng]

my truck failed to start about a week ago at about 4am and also refused to start again at about 4pm. while the engine was cranking it gave a chug and a backfire, so i thought maybe the pump was on its way out, just not completely yet. and then a couple of days later it started as if nothing happened. checked fuel pressure at idle in park is 57psi, when revved it goes up slightly and drops down to about 55psi. shut off for a few minutes it will sit about 64psi and slowly drop to about 61psi. the pump was replaced about 4 years ago with a delphi unit but i havent touched the injectors or anything else. do these numbers seem low? could it be injectors or should i look elsewhere? truck is a 97 k1500, thanks in advance

No, those numbers look good. I don't recall if they give any fuel pressure while running, but with key on/engine off the specification is 60-62. You meet that.

Running wouldn't matter anyway, since you have a hard start problem...

What does your truck do? Just cranks and never fires?

There's something about removing a spark plug wire when it does this and it's supposed to start. I've read that somewhere here, but never tried it. Maybe someone can chime in on the spark plug number...

 

[Nad_Yvalhosert]

There's something about removing a spark plug wire when it does this and it's supposed to start. I've read that somewhere here, but never tried it. Maybe someone can chime in on the spark plug number...

"Hard to start/no start" on 8 cyls and you suggest it'll start easier on 7?
Is that like testing a 9 volt battery on your tongue?

 

[Nad_Yvalhosert]

O.P.: you mentioned 4AM. What's the significance of 4AM?
Does it start perfectly fine at 3AM?
What about 5AM?

What was the weather like? Vortecs have a known problem with old age and humidity induced moisture in the distributor cap...

 

[Nad_Yvalhosert]

A couple years ago I was having trouble starting my 5.7 Vortec if it sat more than 3 days.
Plugs would foul during the winter, never had a problem during the summer. Every couple weeks: no start.
Throw in new plugs and "We're off the green flag racing!"

I ended up installing an MSD box, a set of hotter range plugs, and 2 new upstream O2 sensors. No problems in 3 winters, and 1.5 MPG boost for the win.

 

[stutaeng]

"Hard to start/no start" on 8 cyls and you suggest it'll start easier on 7?
Is that like testing a 9 volt battery on your tongue?

What, you don't believe in miracles?! <jk>

I "think" it has to do with a terminal inside the distributer cancelling or shorting out or something like that. Maybe @Schurkey can explain it if he knows what I'm talking about.

I agree about the moisture: I suffered from a crank/no-start on my old '99 1500 4.3 Vortec for a long time. My issue was guaranteed to occur when it was damp/raining/humid. I never figured it out, but suspected distributer doing something similar to what I mentioned above; I had gone through and changed/checked all electrical components over that time. The only part I wasn't really able to check was the distributer, which had been replaced once. Towards the end I bought a larger battery and I discovered I could get it to start by cranking non-stop for about 1 minute. My suspicion was that dried any moisture inside the cap enough to get a good spark jump and cleared the flooding from all the initial cranking. That obviously wasn't ideal, and that engine had low oil pressure, so it eventually got swapped for a 5.3 Vortec. I don't know if that helps the OP any or not, but that was my experience

Interestingly, the 5.7 on my K3500 GMT400 doesn't have this issue, but I see a lot of other crank/no-starts here on these engines here. When I changed the spider injectors on my 5.7 I noted the distributor cap had a small crack (looked original too), I skeptically reinstalled it, because I was too scared to try an aftermarket one...