One last shot... Breaking up!

[BoostedSUV]

Re: One last shot... Breaking up!

How would fuel volume consistantly cause an issue at 1500, 1900, and 2500 rpms at cruising speed but I have a perfect running truck at 18psi and WOT throttle? I think if volume was an issue it would suffer more under power than bringing rpms up slowly in nuetral....

 

[Luke]

Re: One last shot... Breaking up!

your right I as just pissing in the wind, lol

 

[BoostedSUV]

Re: One last shot... Breaking up!

your right I as just pissing in the wind, lol

Lol ok. I'm taking every suggestion into consideration since I am truely stumped right now. Thought maybe I was missing something or over thinking it. :tup:

 

[SloGN]

Re: One last shot... Breaking up!

ok have you scoped the ignition system?



one thing you could to is use a timing light and try ad find out what cylinder is miss firing. if it's on all of them the coil could be going bad or the dist shaft could be worn and moving around at a constant rpm VS rising/falling rpm. also if you have a adj timing light you could see if the timing ist being very erratic to see if it changes dractically on the timing mark on the balancer


then it may be time to start checking the injectors.

 

[SloGN]

Re: One last shot... Breaking up!

Another thing I forgot to mention... the truck will not do this in OPEN LOOP it only starts doing it in CLOSED LOOP and the warmer the engine temps get the worse it breaks up.

This truck used to have this issue years back where it would go LEAN and break up before I began tuning it with Nolan. We were able to "tune it out" where it would stop breaking up at these very same RPM's and now it's back doing it again and the same spots.

is the factory o2 sensor still there and showing to be working? have you tried a diffrent chip just in case that one may be corrupted?


closed loop threshhold is done by coolant temp/o2 feedback, is the coolant temp sensor reading correct.

 

[BoostedSUV]

Re: One last shot... Breaking up!

ok have you scoped the ignition system?



one thing you could to is use a timing light and try ad find out what cylinder is miss firing. if it's on all of them the coil could be going bad or the dist shaft could be worn and moving around at a constant rpm VS rising/falling rpm. also if you have a adj timing light you could see if the timing ist being very erratic to see if it changes dractically on the timing mark on the balancer

.
then it may be time to start checking the injectors.

That is a good thought and I like the concept but how would I go about doing this? The timing mark on the balancer cooresponds with TDC of #1 cylinder. If I connect the timing light to any other cylinders plug wire I will not have a mark to go off of unless I find Tdc of each cylinder and mark it. Unless I'm wrong here that's how I understand it. Would be a good thing to check for though, I'm going to ponder that thought

 

[BoostedSUV]

Re: One last shot... Breaking up!

is the factory o2 sensor still there and showing to be working? have you tried a diffrent chip just in case that one may be corrupted?


closed loop threshhold is done by coolant temp/o2 feedback, is the coolant temp sensor reading correct.

I have tried a few different chips, all with the same results. I even burned a chip that keep the truck in "open loop" and that accomplished nothing. The factory O2 is in place and it's reading coorespond with my widebands readings. I have looked into the temp sensor as well and according to DataMaster it appears to be reading perfect.

 

[SloGN]

Re: One last shot... Breaking up!

That is a good thought and I like the concept but how would I go about doing this? The timing mark on the balancer cooresponds with TDC of #1 cylinder. If I connect the timing light to any other cylinders plug wire I will not have a mark to go off of unless I find Tdc of each cylinder and mark it. Unless I'm wrong here that's how I understand it. Would be a good thing to check for though, I'm going to ponder that thought

scoping the ignition timing to see if it has erractic changes can be done using the #1 cylinder and the balancer.

but you can check to see if the misfiring is on all of the othe cylinder just ny looking at the light flashing itself it should remain very steady in it flashing pattern with no drop outs. it if starts dropping out that means it's igniton related on that cylinder. if all of them do it is would start looking into the dist be bad even tho it's fairly new.


if ya want yo can call me and i can explain it to ya in more detail

pming you my #

 

[BoostedSUV]

Re: One last shot... Breaking up!

scoping the ignition timing to see if it has erractic changes can be done using the #1 cylinder and the balancer.

but you can check to see if the misfiring is on all of the othe cylinder just ny looking at the light flashing itself it should remain very steady in it flashing pattern with no drop outs. it if starts dropping out that means it's igniton related on that cylinder. if all of them do it is would start looking into the dist be bad even tho it's fairly new.


if ya want yo can call me and i can explain it to ya in more detail

pming you my #

I got you, that makes perfect sense. According to DM timing shows steady around 44 degrees (in park at 2500) but that is an overall number and not each individual cylinder. I do have an adjustable timing light with a pretty big "swing" in timing. I could probably disregard the number and just line the pointer up with the TDC mark and watch for erratic timing at each cylinder as well watch for spark drop out by watching the consistancy of the flashing light. Excellent thought! :tup: I got you PM and if I run into any confusion I will shoot you a call. Thank you for the idea! I will check this tonight, its one more "easy" test to determine or eliminate things. I want to change injectors but I'm not convinced it's fuel related. I think its ignition related but its so weird that it's so consistant and not random.

 

[leadfoot]

Re: One last shot... Breaking up!

How would fuel volume consistantly cause an issue at 1500, 1900, and 2500 rpms at cruising speed but I have a perfect running truck at 18psi and WOT throttle? I think if volume was an issue it would suffer more under power than bringing rpms up slowly in nuetral....

Theoretically, if you had a bad oil pressure sensor which intermittantly failed (eg. 1500, 1900, and 2500 rpms ), it would stop the fuel pump relay -causing you to run lean.

However, (theoretically) at WOT the oil pressure may be strong enough to override the faulty sensor and give the signal to the fuel pump relay to keep the pump on.

 

[Windedv6]

Re: One last shot... Breaking up!

How would fuel volume consistantly cause an issue at 1500, 1900, and 2500 rpms at cruising speed but I have a perfect running truck at 18psi and WOT throttle? I think if volume was an issue it would suffer more under power than bringing rpms up slowly in nuetral....

I don't know if you checked your return fuel line. If it is kinked or partially blocked you could run rich at cruising speeds because your pump would be giving more fuel to the motor that it could not use (which needs to be returned). At higher power ranges the motor uses more of the fuel and doesn't return as much to the tank.

You will return more fuel back to the pump under Idle and crusing than you will under power loads.

John

 

[BoostedSUV]

Re: One last shot... Breaking up!

Theoretically, if you had a bad oil pressure sensor which intermittantly failed (eg. 1500, 1900, and 2500 rpms ), it would stop the fuel pump relay -causing you to run lean.

However, (theoretically) at WOT the oil pressure may be strong enough to override the faulty sensor and give the signal to the fuel pump relay to keep the pump on.

I contemplated this idea... Even though my oil sender is fairly new. I hot wired the fuel pump relay with the test wire and tried running the truck that way. That should eliminate that theory if I'm not mistaken.

 

[BoostedSUV]

Re: One last shot... Breaking up!

I don't know if you checked your return fuel line. If it is kinked or partially blocked you could run rich at cruising speeds because your pump would be giving more fuel to the motor that it could not use (which needs to be returned). At higher power ranges the motor uses more of the fuel and doesn't return as much to the tank.

You will return more fuel back to the pump under Idle and crusing than you will under power loads.

John

I never did physically examine the return line but I still find it hard to believe that could cause my symptoms at the same RPMs. I would think the fuel pressure would show some signs if this was the case. I could be wrong and I will take a look tonight.

 

[BoostedSUV]

Re: One last shot... Breaking up!

Ok I tried what SloGN suggested... I ran the timing light sender off of each spark plug wire and brought the RPM's up to look for a miss. The light never skipped a beat on all 6 cylinders and the truck was at a steady 45degrees on #1 and #5 which make sense since they are 180 degrees apart. That eliminates Distributor, coil, cap, rotor and wires... Of course I can't tell what the plugs are doing but I'm doubting they are the issue at this point.

I'm thinking of changing the Fuel pump even though I doubt that is the problem unless I'm sucking air somehow? Maybe injectors are bad? any way to test them on the truck?

 

[qbnkiller]

Re: One last shot... Breaking up!

Just a couple of months ago, I had the fuel return line pinched off. Driving it around, it caused a fuel starvation issue - not rich spike. I was actually stranded out on the side of the highway. It sputtered, ran like shit, then died. I was tracing the fuel lines with a flashlight when I realized that in the 111th time I had the stock tank in and out, I pinched the fuel return (top of tank) in-between a strap. I loosened that strap completely and the truck fired right up.

I actually drove it around this way for about 2 months. Fixed it right before Nats.

I had a similar problem with the FP dropping as I cranked on the regulator. I spent 2 hours on teh dyno tearing apart my AFPR (Aeromotive - recalled one). After looking more thoroughly, I found out that the fuel pump was loosing pressure under boost. If you crank the pressure, the pump works harder. If it doesnt make pressure, its toast.

 

[BoostedSUV]

Re: One last shot... Breaking up!

well I know my truck has a knock-off walbro pump in it (didn't know any better 4 years ago) and I know I twisted one of the fuel lines on the sending unit and it actually leaked. I JB welded it and never had a problem. Again this was 4 years ago. I'm really thinking about ordering a new Sending unit assembly and walbro pump from Racetronix for a piece of mind. Even though my Fuel Pressure doesn't drop off during the problem RPM's and it rises and falls as it should. It's one of those things that has bothered me so maybe its best I change them...

 

[SloGN]

Re: One last shot... Breaking up!

how long have you had the 50's in the truck?



Matt little had a very simalir problem with his ty.The truck would get a lean miss and run like crap. The only way we could take care of the problem was set the fuel pressure @ 55 line off.

We fought this problem for a while. I then suggested that we flow the injectors. We actually flowed several sets of the delphi 50's and they flowed anywhere from 42-46 lb/hr with a fuel pressure of 43.5.

if one will search his name and look he has posted the info.

here is the link http://www.syty.net/forums/showthread.php?t=66130

 

[BoostedSUV]

Re: One last shot... Breaking up!

how long have you had the 50's in the truck?



Matt little had a very simalir problem with his ty.The truck would get a lean miss and run like crap. The only way we could take care of the problem was set the fuel pressure @ 55 line off.

We fought this problem for a while. I then suggested that we flow the injectors. We actually flowed several sets of the delphi 50's and they flowed anywhere from 42-46 lb/hr with a fuel pressure of 43.5.

if one will search his name and look he has posted the info.

here is the link http://www.syty.net/forums/showthread.php?t=66130

The 50's have been in the truck for a few years and about 30k miles. Honestly the truck never drove great with these injectors. I put them in when I beefed up the motor and turbo. Prior to doing so, when everything was stock the truck ran and drove great! Unfortunately a rod came out the pan so I stepped everything up...

the more FP i add the worse the trucks breaks up. If I drop it down to 30 the miss just about goes away. Unfortunately that FP is too low to safely run at.

I just ordered a Sending unit assembly and Racetronix Walbro. Doesn't hurt to change them anyway.. Matt

 

[Quickstop [UK]]

Re: One last shot... Breaking up!

Hmmm..

I had an issue where my 50#s would let the truck run PERFECTLY with NO fuel pressure but the second I plugged the pump back in and tried it, the cylinders were flooded and it wouldn't run.

I got 3 different ECMs and various BINs for 50s and it was crap.

I bit the bullet and went with the 65s and the truck runs great now. I did get a Moates as well but even with the 50#s, if it was the ECM then they should have run on a stock tune.

My theory was that the 50s were very susceptible to being open and the vacuum from the cylinder was drawing in enough fuel to allow it to idle.

Try priming it then diconnecting the FP relay and trying to start it. If it starts then you've got your answer.

50#s seem like nothing but a pain.

 

[BoostedSUV]

Re: One last shot... Breaking up!

You're not the first person to have issues with the 50s... That's my next move is to step up to 65s. I just can't decide if I should take my chances and buy used or bite the bullet and buy new ones. That's my next move... Truck never ran great since I put them in.