Key on for 8 minutes before starting.

[venuspie1]

Still trying to figure this out without throwing parts at it. When I turn the key on the fuel pump runs longer than the normal 2 second cycle. It run between 7 and 8 minutes every time. During this time the truck will not start. As soon as the pump stops running. Truck starts and runs perfect until the next time it sits for 30 min or so. While the pump is running, I’m getting 40psi of pressure but still won’t start until it stops. Any any ideas?!?
Thanks

 

[Curious Hound]

Gonna have to ponder that a minute. My first instinct is that fuel pump is having trouble building pressure.

 

[Uncle Gump]

What happens if you cycle the ignition?

Does the fuel pump still act that way or work as normal?

I would first look at the relay connections for any corrosion... and just try a new fuel pump relay.

 

[venuspie1]

Have tried relay and no change. What’s confusing me is that I have 40psi from the get go but if pump is running it won’t start. However I can start it with starting fluid and it will crank but runs rough. Sounds like it has a cam and puffs bluish white smoke. Check engine light comes on with code 122. TPS. Put new tps on and no change. After 8 min of running rough, check engine light goes off and everything is good

 

[Uncle Gump]

Stange indeed...

If it starts on starting fluid... that would make one think you aren't getting injector pulses.

Might be worth buying a noid light to test for injector pulses during crank. Same test could be checked with a test light.

 

[Uncle Gump]

Just a tip from old man Gump...

Many times when strange things happen they can be attributed to poor grounds. Also... many electrical problems are caused by those poor grounds and bad connections.

Not saying a poor ground is your problem but that relay running constantly... could mean the relay control circuit is finding a sneak path to ground somewhere it shouldnt be. All that could be caused by a poor ground at the PCM.

So you've ruled out a stuck relay and the connections are good. The next thing I would be looking at is your grounding points.

I don't have schematics for that year truck to tell you where they all are.

Also... don't forget the good old wiggle test. With the fual pump acting up... try wiggling harnesses... connections.... ground points to see if you can make the conditions change.

 

[Shran]

I think RonD and a couple others were having problems with fuel pumps that eventually traced back to bad capacitors in the ECM. You might open it up and inspect those.

 

[venuspie1]

Just a tip from old man Gump...

Many times when strange things happen they can be attributed to poor grounds. Also... many electrical problems are caused by those poor grounds and bad connections.

Not saying a poor ground is your problem but that relay running constantly... could mean the relay control circuit is finding a sneak path to ground somewhere it shouldnt be. All that could be caused by a poor ground at the PCM.

So you've ruled out a stuck relay and the connections are good. The next thing I would be looking at is your grounding points.

I don't have schematics for that year truck to tell you where they all are.

Also... don't forget the good old wiggle test. With the fual pump acting up... try wiggling harnesses... connections.... ground points to see if you can make the conditions change.

Checked all the grounds I could find. Funny enough the wiggle test actually helped me realize it takes eight minutes for it to shut off. I probably would’ve never known that if I’d just turn it on and leave it on and start tinkering under the hood.

 

[venuspie1]

I think RonD and a couple others were having problems with fuel pumps that eventually traced back to bad capacitors in the ECM. You might open it up and inspect those.

That I will have to google. Not sure where the ECM is or that there were capacitors inside. The capacitors themselves can be replaced?

 

[alwaysFlOoReD]

That I will have to google. Not sure where the ECM is or that there were capacitors inside. The capacitors themselves can be replaced?

They can.

 

[Uncle Gump]

Checked all the grounds I could find. Funny enough the wiggle test actually helped me realize it takes eight minutes for it to shut off. I probably would’ve never known that if I’d just turn it on and leave it on and start tinkering under the hood.

If I'm not mistaken... there is a body ground right next to your PCM in the lower kick panel.

I still think checking for injector pulses while it cranks and won't start is a worthy test. It might not tell you what it is...but could tell you what it isn't.

 

[venuspie1]

I will work on that and report back. Thank you!

 

[4x4junkie]

I think RonD and a couple others were having problems with fuel pumps that eventually traced back to bad capacitors in the ECM. You might open it up and inspect those.

I think Shran might have this one here (I was thinking the same thing... This is just weird enough that it's probably not any of the usual culprits).

The symptoms seem about right for it too (failing caps are at their worst when cold/first turned on, as things get warmer, their function tends to come back up a little bit).

 

[venuspie1]

Finally got around to removing the ecu. Here are some pics of the capacitors. They are not bulging but a couple have some blue residue around them. I know nothing about these things or even own a soldering iron!

 

[venuspie1]

Also while removing this, I found a couple more grounds but all looked good and tight