Fuel Delivery/ TPS Sensor problems

[bobbywalter]

The power loops back to the switch after the HP pump. Uaually Goes from pink to red and another color from there...

Goes battery to fuel pump relay.

Fuel pump relay to inertia switch

Inertia switch to HP rail pump.

T from. There to switch.

The switch sends power to the low pressures in Tank.

Splitter valve changes gauge feed.



Fuel psi is the most important tool for this system.

 

[bobbywalter]

Should be 0.98-1.01 at idle.

These actually .65 ish.....to.99

 

[aball4620]

Should be 0.98-1.01 at idle.

So when I set the idle voltage to 0.99 with KOEO and start it constantly surges between 900 - 1700 rpm and tries to stabilize around 1600. It also gives me about a 1 second delayed response when opening the butterfly. Most of the posts on this forum and a few others have "normal" idle readings from 0.85 - 1.0. Seems to idle just fine with the occasional stumble after warming up right around 0.80. This is a brand new TPS and while it certainly could be bad, is there anything else that you may be thinking?

I'm in the process of tracking down power to the rear pumps. When I have my ear next to either one and the ignition is turned to the on position I get what sounds like a gurgle, but nothing clicking like a pump. I'm wondering if the gurgle I'm hearing is siphoning from the high pressure pump? Just checked for power to the fuel selector switch and it gives a couple seconds of voltage out of the brown/white wire on the selected side. Now I'm off to see if that voltage is making its way through the harness to the selector valve.

 

[aball4620]

These actually .65 ish.....to.99

So seeing 30 psi at idle - which is at the very low end - and knowing that the high pressure pump is active, but not seeing any changes when switching between the two rear tanks, does this make you think wiring issue? Are there any "most likely" failure points that you know of? Seems like it has to be between the selector switch and the selector valve.

 

[bobbywalter]

This seems like a large vacuum leak or map sensor issue.

Or plugged injectors.

 

[aball4620]

I mean it would seem. Vacuum pressure holds at about 18-19 and drops with opening the throttle. MAP sensor is new, although I've not tested it to confirm that it works appropriately. Injectors are all re-manufactured and I tested them all for both spray pattern and solenoid function before installing. Truck hasn't left the driveway since install. No particulate in the low pressure glass fuel filter between the reservoir and the high pressure pump (after market). Brand new fuel filter after the high pressure pump.

So I'm not sure how the low pressure pump is supposed to get power but here is what I've discovered down stream from the selector valve. This is on the rear tank with the yellow/ lt blue wire. With KOEO and KOER the low pressure pump received power, but the power oscillates about every half second between about 0.2 v and 5.9 v. It just bounces back and forth. And not to consistent numbers, there is sometimes a 3.xx or 4.xx mixed in there. Is the low pressure pump supposed to have the same priming as the high pressure pump and/or constant power?

 

[bobbywalter]

Hmmm.

That is a problem.






Fuel rail itself will murder brand new uncranked injectors. Rots on the inside.


Run straight power to pump. Just a 30 foot spool and a good ground.

 

[bobbywalter]

I suspect your HP pump is giving you air pressure and it is a volume issue...

Your spools in the diverter may be bleeding by too.

Good news....get solid stream to the rail pump....and it will scream.

 

[aball4620]

Hmmm.

That is a problem.






Fuel rail itself will murder brand new uncranked injectors. Rots on the inside.


Run straight power to pump. Just a 30 foot spool and a good ground.

When I installed the heads I painted the rail. Now obviously I couldn't see through the whole thing and never even considered getting out the borescope, but it didn't look particularly rotten.... Hopefully that isn't what is going on. I can always pull the injectors and see if they're plugged up.

So you're saying I should just hard wire the rear fuel pump and see how it reads? Is that to say it is supposed to be continuous voltage? When things blew up and started this whole mess I ended up tracing the fuel back pressure to the selector valve that had more or less clogged up on the return side. That was replaced, and while it ran like garbage before replacing and ran a little better after I'm still in this position. Might it be that the selector is malfunctioning?

 

[bobbywalter]

I would pop off intake side of HP pump and run it in gas can...and disco rear pumps.....cycle it till it primes and see how it runs.


Then rebuild all the low pressure wiring and valving.... switching....the switch may be the voltage drop.

 

[aball4620]

I suspect your HP pump is giving you air pressure and it is a volume issue...

Your spools in the diverter may be bleeding by too.

Good news....get solid stream to the rail pump....and it will scream.

I just want to make sure I'm understanding before I start tapping into fuel system wiring. What do you mean by giving me air pressure? I did pull the pump months ago and checked it on the bench. It indeed fired up with straight voltage, but I haven't checked it as such when hooked up to the fuel system.

 

[aball4620]

Checked voltage up and down stream from the selector valve. Chilton's diagram has front tank up stream red and down stream blue/yellow. Rear tank up stream brown/white and down stream yellow/ lt blue. I get the same erratic voltage reading on the front tank down stream blue/yellow wire. Both the up stream red and the brown/white measure a nice even 13+ volts with the engine on. Looks like the selector valve might be the problem not allowing the low pressure pumps to come on. And I'm probably teetering on burning them out letting it run that way. Seems like the reservoir is getting filled just enough to keep things somewhat functional when idling but not enough for actually revving past about 1500.

I'll get back to you on the hard wiring to the low pressure pumps. I would imagine there is a way to bypass the selector valve with the signal coming directly from the selector switch. Are the pumps supposed to receive full voltage or are they supposed to drop down to around 6? I could also just do a tank delete and be done with it.

 

[bobbywalter]

Full voltage is fine. Preferred.

The HP pump is obviously cavitating and your not getting proper volume.


You can have 30 psi with low volume with many of the rail style pumps....my old t Rex would literally read 35 psi air/partial fluid.

As in attach a psi gauge to output completely dry...put power to it and 20 plus psi totally dry....with fluid 90 psi dead headed...it was a 355 lph pump though. Stock is like 60 lph.

 

[aball4620]

Full voltage is fine. Preferred.

The HP pump is obviously cavitating and your not getting proper volume.


You can have 30 psi with low volume with many of the rail style pumps....my old t Rex would literally read 35 psi air/partial fluid.

As in attach a psi gauge to output completely dry...put power to it and 20 plus psi totally dry....with fluid 90 psi dead headed...it was a 355 lph pump though. Stock is like 60 lph.

So full voltage to the rear pump changed nothing. Was maybe even more hesitant to rev, but engine had cooled a bit too.

If the high pressure pump is doing that is it just toasted?

 

[bobbywalter]

Not what I am saying....seems air locked.

You need to do a volume test or just run the HP pump like I described earlier to eliminate all of the valving.

Rember your working with gas.

I keep a rail pump and fittings just for external testing.


Easiest way for me is to pop the return and feed....feed and return it from a container/can. Ground the 22 so the pump stays on and see what psi is

It's possible the return line is stuck shut and dead heading the.low psi pump giving you 30 psi and the rail pump is dead.


Lots of potentials