Fuel Delivery Issue

[berzerker]

Re: Fuel Delivery Issue

Without being rude to anyone. When I bought the truck a year ago, took it to RPM. $2.5k later, truck still ran poorly. They couldn't figure it out then. I have since replaced pretty much everything and narrowed it down to fuel.

ok ... nevermind then . it's has to be something simple with the fuel delivery . i'm with tom here . start over at the fuel pump . new pump / fuel gauge sending unit harness , new correct rubber junction hose between pump ( make sure to use sae graded line " j30r10" ) . proper voltage to fuel pump , ecm voltage at a steady 13.5 v or higher . has the alternator been tested ? ecm voltage mod may be a good upgrade . these basics can make or break a truck running wise . my dd ty has had all this corrected and always runs pretty decent .

 

[tphilpot]

Re: Fuel Delivery Issue

Yipee! Get to drop the fuel tank again! I will investigate this. Thanks for the tip.

 

[tphilpot]

Re: Fuel Delivery Issue

Curious question. I have been retracing my steps and before I drop the tank, etc. I wanted to know if a faulty Throttle Position Sensor could cause all of the injectors to be open. All that you guys have mentioned points to some sort of issue in the tank (which it could be) but that would not cause the fuel to flood into the cylinders? Earlier in the thread I mentioned taking all the plugs and and they were all wet with gas as well as being pitch black.

I am a rookie, but it seems to me that something in the system is telling the injectors to stay open. What's more, I looked at a DM file I did a few weeks back and the RPMs were rising and in the middle of that the computer reported the TPS% and Voltage as both dropping (and Boost). Note when this occurs the RPMs are still increasing?? See enclosed capture.

Thoughts?

 

[RealFastV6]

Re: Fuel Delivery Issue

Seems plausible based on the pic.

On the pic; were the other "dips" in the TPS you feathering the throttle or did you have it at WOT the whole time? Trying to get an idea if we're only concerned about the 1 dip or the entire line.

 

[The Bronze]

Re: Fuel Delivery Issue

The TPS drop, if it really wasn't caused by your foot-feed, won't cause the injectors to stay open. It could cause the injectors to shut off (Decel enleanment) though. It serves more as an anticipator and doesn't have the fuel control that RPM & MAP has.

I tried to look at your old DM files on your past threads, but none were valid. Can you reload one and link to it here?

 

[Don W.]

Re: Fuel Delivery Issue

Off the wall comment: the TPS does not have a "direct" link to the throttle. The throttle pushes it open and spring within the TPS causes it to "follow" the throttle when the throttle is reduced. Look at it and this will make sense. That little lever on the throttle shaft could be loose. (Long shot but what the heck.)

Check that the TPS is operating smoothly, Check the connection at the TPS. (Meaning remove it and physically look at the connector. Prolly some electrical tape around the first few inches of the wires, remove that and inspect.

Hook up DM, turn key on (motor off) and slowly depress the gas pedal. TPS readings should be linear and vary from .2 volts to over 4.5 at full throttle.

No I don't know all this stuff, Manual is right in front of me... :rotf:

 

[RealFastV6]

Re: Fuel Delivery Issue

The TPS drop, if it really wasn't caused by your foot-feed, won't cause the injectors to stay open. It could cause the injectors to shut off (Decel enleanment) though. It serves more as an anticipator and doesn't have the fuel control that RPM & MAP has.

Good point, however, the boost line (map) dips also... and guess what the map sensor and the TPS sensor have in common?

:tup:

 

[The Bronze]

From the single point in time, it looks like the throttle is lifted and boost falls. Am I missing something else? That shot is just inconclusive to me.

 

[RealFastV6]

Re: Fuel Delivery Issue

Phil, was your foot planted or were you feathering the throttle (at all) ?

At this point after reading through your old threads I would strongly suggest you triple check grounds - specifically rear drivers side head. If you're having both sensor issues (TPS and MAP dropping) and injector fail-to-close issues (wet plugs) then grounds seem like a likely culprit.

DaveP posted a good list here: http://www.syty.net/forums/showthread.php?t=58556

 

[tphilpot]

Re: Fuel Delivery Issue

Answer to the question. If I was pushing the throttle any harder I would have given Fred Flinstone a run for his money. No fanning at all.

Gonna check that ground now.

Thanks for the tips guys.

 

[Don W.]

Re: Fuel Delivery Issue

As I read the manual these all ground through the ECM and the ECM grounds at the left rear of the engine and the left front (intake). Assuming those are good. I'd consider dropping the ECM and checking those connections as well.

 

[tphilpot]

Re: Fuel Delivery Issue

Thanks. I have checked the grounds. I can only feel the ones on the back of the left head. There are 3 as opposed to 2 as per the thread on grounds. Tan, Black & White and a larger black one.

The two grounds on the forward left side on attached to the bolt that holds to water inlet to the intake--can't see that that would make a difference, but I will move them anyway.

I have dropped the EMC a couple of times now. I will check in particular the ground wire this time. Haven't seen anything stand out before.

 

[RealFastV6]

There's a thread somewhere with instructions for checking your TPS sensor voltage with a voltmeter. Verify that you're getting not only a good ground, but also 5V reference at the TPS sensor.

 

[tphilpot]

Re: Fuel Delivery Issue

Will check that out. I have a manual that tells me the process. Thanks.