HELP 98305chevy fuel injection issues

[Nice98chevy]

As per the tittle I'm having problems with my fuel injection. I have a 98 chevy pu 305 that within the last year I replaced the fuel injection pump (Delphi unit) and have started having issues with. The first thing that happened is I started to have issues with the pump not holding pressure after being shut off. It would take a few moments of cranking to build up fuel pressure and then it would fire up. Last week it would not start. I rented a pressure test kit, hooked it up, and it seemed (at first) to be operating as it should. 65 psi at start, dropped to 58 psi when cranking, and still no start. About 5 days later I had it towed into the shop and they got it to fire up in the parking lot, although it stumbled at first. Their conclusion is that the fuel pump is "at the minimum spectrum of psi".

Does this sound right to you?

 

[GoToGuy]

Why did you rplace the pump in first place. Electrics power and grounds. Fuel pump relay. New fuel filter. Pressure before filter? Pressure at Spider? Upgraded injection? Where did, what did they test to give diagnosis?

 

[Nice98chevy]

The previous pump was working but the fuel gauge was not. It was an ACDelco made in China. It is the second pump that I have installed. My truck has 207,000 miles on it. The fuel filter was replaced. It's fine There are no other problems (that I know of) with the fuel system. When it runs - it runs perfect. The fuel pressure was tested (I assume) at the fuel pressure test fitting on the metal fuel line. I picked it up from the shop a few days ago and it's been running perfect until this morning when it wouldn't start again.

 

[Nice98chevy]

I am trying to determine if it's the pump or the fuel pressure module in the intake manifold. That's the best I can determine when searching for the answer. It has stumbled or had difficulty starting when I've try to start it but I'm leaning towards the fuel injection pump. The truck, once again, runs fine once it fires up. The Delphi unit I installed "should" be good.

HELP

 

[Frank Enstein]

Shurkey is bound to say "Get some live data from a good code scanner so we can see the issues in real time."

Merry Christmas Shurkey! I saved you some typing!

In all seriousness we really need specifics to help. So here are some quick and dirty things you can check for (nearly) free.

Check for spark. Remove the coil wire from the distributor, put an HEI spark tester or at least a spark plug "borrowed" from the lawn mower in it and set it on a good ground (jumper cables work well for this). Crank to see if it has sparks.

Next remove/inspect/replace the cap and rotor. They are a known problem. Check for carbon tracking, and burned spots. Brass terminals are a must. AC Delco or Standard Motor Products/Blue Streak are what I buy.

Temporarily disconnect (GENTLY! they can be brittle) the coolant temp sensor (two wires) to see if it will start. Unplugging it tells the computer that the coolant temp is -40 degrees F. This will make a very rich mixture to help it start.

That is only for a test do not leave it that way. If the coolant temp sensor is partially or completely shorted it tells the computer that the engine is warmer than it is and it doesn't add enough fuel for a cold start.

Check the plug wires with an ohm meter off the engine one at a time. The resistance should be <1000 ohms per foot.
The resistance doesn't matter as much as long as the value doesn't change when the wire is wiggled like a snake.
Check the coil wire the same way. It works 8 times as hard as the others.

If the resistance changes that is an indication that the wire should be replaced.
Another indicator that the wires are bad is voltage leakage. Spray the wires with a 50/50 mix of Windex and water and start it up in the dark. This will make any voltage leaks easier to see.

Check the spark plugs. Damage/wear/dirty? Replace them. I recommend platinum for longer service life. NGK for me.

Good Hunting!

 

[Nice98chevy]

I appreciate what you are suggesting ... but ....everything you have suggested seems to be fine. The truck runs great. I've done a complete tune-up, plugs, wires, cap, rotor ... etc. It runs fine as long as I get optimum fuel pressure.

 

[Schurkey]

Shurkey is bound to say "Get some live data from a good code scanner so we can see the issues in real time."

Merry Christmas Shurkey! I saved you some typing!

If a person likes me, I'm consistent. If a person doesn't like me, I'm predictable.

As per the tittle I'm having problems with my fuel injection.

I don't think you know that for sure. Yes, it's possible that the "injection" has problems...just as possible that it's something else.

I have a 98 chevy pu 305 that within the last year I replaced the fuel injection pump (Delphi unit) and have started having issues with. The first thing that happened is I started to have issues with the pump not holding pressure after being shut off. It would take a few moments of cranking to build up fuel pressure and then it would fire up.

Not holding pressure could be the fuel pump...or it could be the pressure regulator at the spider system in the intake manifold. It could also be a leaking injector. Remote chance it's an external leak due to rusty or damage fuel plumbing.

More testing needed.

Last week it would not start. I rented a pressure test kit, hooked it up, and it seemed (at first) to be operating as it should. 65 psi at start, dropped to 58 psi when cranking, and still no start.

Have you verified that your fuel pressure tester has an accurate gauge?

One of mine is off a few PSI, enough that I don't trust it any more. Bought a new stand-alone gauge from Amazon, but haven't installed it on my tester yet. And once it's installed...I still have to compare it to a couple of gauges I trust to see if it's accurate/repeatable.

About 5 days later I had it towed into the shop and they got it to fire up in the parking lot, although it stumbled at first. Their conclusion is that the fuel pump is "at the minimum spectrum of psi".

Does this sound right to you?

No. Did they TEST the pressure, or are they making a wild-asp guess? Doesn't sound to me like they've done any real diagnosis, they're just "winging it".

 

[GoToGuy]

When someone states " i tested it, 60 psi" we take that as " you took action and got a result". Alot of the questions asked are the same questions the service manual would ask to check or test. But we can skip a few by asking some pointed questions for verified answers, not seems, or maybe.

 

[stutaeng]

Oh man, another fuel pump replacement and the darn thing still isn't fixed. I keep recommending getting the injectors, FPR checked and reading fuel pressure while under load. Members are probably tired of my responses too but otherwise you'll most likely spend a good chunk of cash fixing this.

The bad fuel pressure gauge is a valid mistake. The other day I was messing with my truck and hooked up my backup pressure gauge (main guage developed a leak on the hose) and it showed zero pressure. What the heck, I thought? Truck ran before and I was changing my intake... I removed the fitting, poked the shrader valve on the intake and a gush of fuel came out. What I had forgotten is that backup guage came with the little fitting inside missing! Basically, I got junk from overseas!

I think further diagnosis needs to be performed. I would focus on the FPR and injector. If you need to open up the plenum and physically observe for any fuel leakage. Less common is for the FP checkball to be leaking,based on what I read.

BTW, this is not happening when it is damp or humid, is it? I'm not sure why this sometimes affects some these generation of Vortec engines.

I hope the issue gets resolved!

 

[Frank Enstein]

If the pump pressure changes from normal numbers on cold start, trace the electrical for the pump. hotwire the relay and see if wiggling the wires changes the pitch of the pump.