• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Ok...now im totally stumped!

Darkrider

Darkrider

Lobo Solitario
Messages
240
Reaction score
4
Location
Lloydminster, SK Canada
Ok I have been having a problem with my truck for awhile now and as a result have been unable to drive it for the past two weeks. The problem is it seems like it goes into a fuel starvation situation after 20-40 min of driving. The first time this problem showed up was about 4 weeks ago or so when i washed the truck. When it happened that time i thought it was due to something getting wet in the car wash. Then i realised it had been sitting idling for 20 min prior to that. That is what led me to suspect the beaten up old PMD that was mounted in the air box. Now the problem has reappeared after 40 min of driving after i installed the brand new PMD/Relocation kit from Leroy....:mad2:

What happens after 20-40 min is this:

It starts off with not wanting to rev over 2800-3000 RPM
Then it starts to surge
then it wont idle at all and i have Zero throttle response.
Then after the truck sits anywhere from an hour to 2 hours it goes back to normal for a bit..then starts the entire cycle all over again.

The Injector pump in the truck is the original from the original engine. So its a known good part.
The PMD has been replaced and relocated.
A new fuel filter was installed during the winter and has less then 10000 km on it
If i crack the bleeder valve on the FFM it has a steady stream of fuel like old faithful.
About all i can think of now is swapping the '95 Computer in the truck now for the original '94 computer or its time for a new lift pump. Kinda wondering if all the gelling problems i had in the winter finally killed the lift pump. Every thing points to it being a fueling issue.
 
have you tried loosening the fuel tank cap? also put a guage on there where you can see it while your having issues ( taped to the wiper works) and monitor the fuel pressure. you haven't mentioned anything about your OPS so I'm assuming you haven't changed it, it could be giving you an intermittent problem running your LP. Also could be a plugged tank sock
 
The OPS has been bypassed. All it does is send signal to my op gauge and that's it. Previous owner ran a wire from the LP to the fuse box so it is triggered when the key is on. Next pay day i plan on getting some bulk wire and a relay then making a relay harness that will still be triggered by the key. On that note will 14 ga wire be heavy enough for that task or should i make it from 12 ga? My original FFM has been eliminated and replaced with one from an old 6.2 truck with the spin on filters. Is there a way to add a fuel pressure guage to that? Just wondering if i can add a T to the output side and thread a gauge to the T for trouble shooting then replacing it with the sensor for an electric gauge in the interior later.
 
Have you tried pluging the PMD right onto the truck harness and eliminate the ext harness. I have a feeling its electrical or the IP
 
Burning oil said:
Have you tried pluging the PMD right onto the truck harness and eliminate the ext harness. I have a feeling its electrical or the IP
Click to expand...

Not yet was too frustrated with it to continue working on it today. One thing that I seen mentioned in various trouble shooting guides is the fuel shut off solenoid can some times give trouble. I will be picking up a spare lift pump from my buddy on wed, almost kinda wondering if it isnt that harness between the ip and the pmd, it was extended to move the pmd to the air box using two old harnesses. The ip itself was swapped just before I bought the truck because it was giving a pump cam reference error. The ip is from the original engine and is a known to be good part.

Sent from my SGH-T959D using Tapatalk 2
 
For sure eliminate the way they extended the harness. Did you get a cable from me? if not plug the PMD into the truck harness to see what it does.
 
Im talking the short IP harness that pluged into the PMD originaly mounted on the IP. Just plug PMD back in (with heat sink) there and see what you get.
 
Burning oil said:
Im talking the short IP harness that pluged into the PMD originaly mounted on the IP. Just plug PMD back in (with heat sink) there and see what you get.
Click to expand...

That is what im trying to explain, the previous owner cut and spliced together two of the original short harnesses (the original one from the pump and one from a spare pump) to make one long one. To do what you are suggesting I will need to remove that afformentioned modded harness and install a new one. This is where I ask...just how much of a pita is that gonna be?

Sent from my SGH-T959D using Tapatalk 2
 
OK I see said the blind man. Do you trust it? If not.......blah blah...... Please tell me they soilderd it and did'int use butt crimps?? (i have seen that).
 
Burning oil said:
OK I see said the blind man. Do you trust it? If not.......blah blah...... Please tell me they soilderd it and did'int use butt crimps?? (i have seen that).
Click to expand...

It was soldered, first thing I asked about it actually, im just wondering if it just didnt go bad or something from a solder joint letting go or weakening when the truck is hot...

Sent from my SGH-T959D using Tapatalk 2
 
A bad cable is known to present alot of different problems. It really needs to be fixed the right way at some point anyway right? so might as well do it now and rule it out. Bad thing is you do need to remove intake and buy a new IP harness.

You could also try wiggling the harness while truck is running and see what happens.
 
Well i took a look at the routing this morning and noticed that the cable was hanging 2" above the heat shield of the Turbo..so i rerouted it towards the front of the motor under the upper intake. I will be testing it later today to see if that solves it.
 
Ok....After another thrash session on the truck the following items were changed:

Swapped the lift pump for a spare
Swapped the ECM for the original from the truck (it was running on the ECM from the donor truck)
Rerouted the extended PMD cable away from the Turbo

End result....

Well most of the problems listed above are now gone only to be replaced by a new problem. I was able to drive the truck for closer to an hour today, Ran it fairly hard in fact while still on the '95 computer but after swapping lift pumps and re routing PMD cable. The new problem that has popped up is now its randomly stalling out. Which points to a fuel supply problem rather then an electronics problem like before. We are gonna attempt to blow air through the return lines tomorrow and possibly drop the tank to swap for a different fuel sending module. at this stage it is pointing to either a blocked return or a blocked up tank sock.

The previous problems:

It starts off with not wanting to rev over 2800-3000 RPM (Eliminated)
Then it starts to surge (Eliminated)
then it wont idle at all and i have Zero throttle response. (Eliminated)
Then after the truck sits anywhere from an hour to 2 hours it goes back to normal for a bit..then starts the entire cycle all over again. (No cool down needed this time, was able to hot start it and keep going for a bit till stalled again)
 
What model IP you got on your truck?
94 model has stock a 5067 IP wich needs the 94 Eprom.
The later models have a diff # IP like 2188(stock)or the 5521(replacement),these pumps need the 95 Eprom to run properly.
 
bison said:
What model IP you got on your truck?
94 model has stock a 5067 IP wich needs the 94 Eprom.
The later models have a diff # IP like 2188(stock)or the 5521(replacement),these pumps need the 95 Eprom to run properly.
Click to expand...

It has both the original IP and the original ecm in
It now. Before it had the '95 ecm in it. It actually does the stalling thing with both ecms now. Which is leading me to suspect I had electrical probs (lift pump) stacked on top of mechanical probs (blocked lines)

Sent from my SGH-T959D using Tapatalk 2
 
You must log in or register to reply here.
Back
Top