Fuel Pump Relay issue...maybe?

[jc98ss]

Results of fuel pressure bleed off confirm slow leak in check valve

Key on, engine off = 62 psi
After 2 seconds drops and holds at 58
Key off drops slowly to 50 psi in 1 minute
5 minutes with key off = 30 psi

My plan is to throw in a new Delphi fuel pump in the next couple of weeks.

 

[doncaruana]

Results of fuel pressure bleed off confirm slow leak in check valve

Key on, engine off = 62 psi
After 2 seconds drops and holds at 58
Key off drops slowly to 50 psi in 1 minute
5 minutes with key off = 30 psi

My plan is to throw in a new Delphi fuel pump in the next couple of weeks.

This is interesting. The shop where I took mine insisted that it held pressure, but I never saw it myself, nor did I ask them if they tested it like you did. I do seem to recall that 58 number though actually, so I wonder if they stopped there.

They also just had the truck for 4 days and insisted they couldn't duplicate the latest version of this, which is that it doesn't stall completely (at least not when I tried it) but it will long crank and/or sputter after starting. When it did that to me, I let it go to see if it would catch up and it did, but my daughter hits the gas when it sputters and it stays running. At an extreme instance of that, it will throw the P0161 code, but doesn't throw it unless one of those hard start instances happen.

I don't have a fuel pressure tester nor do I know enough of what I'm doing to try it myself! LOL. The mechanic at the above shop, who I actually likes, left that shop as of yesterday so I'm done with them and I'll take it to another shop.

Footnote on this shop - I went over there yesterday and one of the owners was being a jerk about me getting the correct VIN programmed. Kept asking if it had the latest code or something. I told him there wasn't a whole lot to the programming of a 97 Tahoe anyway, but yes. Apparently he was PO'd that I prevented him from soaking me for double what it cost him to farm it out. He wanted to charge me $260 and I found a guy (core part of his business, knew what he was doing!) who drove to my house and did it for $135. Anyway, I eventually ignored the owner and don't really even trust these last 4 days because I think the mechanic was under directions not to "find" the problem because that would mean they had to refund me for replacing my VCM.

 

[jc98ss]

Im sorry about your shop experiences....fuel pressure gauge is under 40 bucks on Amazon, i bought the OMT brand, fits all GM....simple to use, Schrader valve on drivers side of intake, super easy....plenty of videos on Youtube.....just change your fuel pump man, use a good one, dont go budget....Delphi or AC Delco....you'll be done with this.

 

[doncaruana]

Im sorry about your shop experiences....fuel pressure gauge is under 40 bucks on Amazon, i bought the OMT brand, fits all GM....simple to use, Schrader valve on drivers side of intake, super easy....plenty of videos online.....just change your fuel pump man, use a good one, dont go budget....Delphi or AC Delco....you'll be done with this.

That's what I want to do! But it's not something I can do myself for sure and I can't even get a place to give me a quote on simply changing it out!

 

[jc98ss]

I hear you but it's not hard brother, youtube will walk you right through it step by step....plus you know some shop didn't put in a crappy budget pump so that you'll have to come back in a year....simple hand tools, a couple jack stands, and a little bit of time....always clean fuel tank out well and replace fuel filter when changing the pump.....if you're not able, im sure there's a shop out there who'll do it, not a rough job at all.

Ill post results once i get mine changed out, if i ever get a day off...might be a while

 

[doncaruana]

Update for anyone still paying attention...
Took it to a different place who actually listened to me and checked the fuel pressure and - lo and behold - it's losing pressure when it sits. If only someone had suggested that at the previous shop...Oh wait...I did. I even had a print out of the discussion from here when that was first brought up.

However, they said they smell gas by the throttle body and therefore think the pressure leak is coming from somewhere there, not the fuel pump. And they actually said they weren't even sure they wanted to tackle that anyway (said "it's a rare problem"). Not sure what I want to try and do next.

 

[east302]

Take a look through the throttle blade and see if it’s wet in the back. It should be pretty sooty up front by the EGR valve and on the injector tubes so ignore that.

You can isolate the supply and return lines to identify the exact source of the pressure loss (injector, regulator or pump)—guess they didn’t want to go that far with it. The way things are now, injector assembly replacement would probably easily hit $1000 at a shop vs $400 or so if you did it yourself with the MPFI version.

 

[doncaruana]

Take a look through the throttle blade and see if it’s wet in the back. It should be pretty sooty up front by the EGR valve and on the injector tubes so ignore that.

You can isolate the supply and return lines to identify the exact source of the pressure loss (injector, regulator or pump)—guess they didn’t want to go that far with it. The way things are now, injector assembly replacement would probably easily hit $1000 at a shop vs $400 or so if you did it yourself with the MPFI version.

One thing on the table at this point is the money I spent on the Ecm. That shop is getting a call from me. That money is spent so if they refund me I can turn it around and get it done right. I just don't have the tools and physicality (not to mention knowledge!) to do something like that myself.

 

[doncaruana]

After talking to them again, they said they smelled gas up where the intake is where it attaches to the center of the motor. I'm not exactly sure what that is supposed to be. They said they didn't particularly rule out the fuel pump, but the fact that they smelled gas there made them think it might be the fuel pressure regulator or the "lines". Not sure exactly which lines those are, not the fuel lines though and he said they are plastic. I know I'm way over my head here, so any help is greatly appreciated...

One additional thought...Back in August, there was a little run where it would make this loud pop sound when starting occasionally. That went away and then Monday afternoon it did it again. But just the once. Not sure if that leans toward the fuel pressure regulator or just weird coincidence.

 

[YukonGTmaster]

Sorry to hear about the problems you are having with your rig. When I installed the upgraded MPFI Spider and Fuel Regulator assembly on my '97 GT, the starting, drivability, and fuel economy was awesome. If it turns out that is what is required in your case, I would consider it money well spent if you want to keep and drive your truck. Good luck!