1997 6.5l issues

H

Headcase98002

New member
Alright, a friend of mine picked up this truck two months ago for $2500. We were told it the fuel level sensor didn't work and fuel tank was empty. We fond a brand new tank, sender and lift pump. All the lines from tank to mid frame were spliced and cobbled together, we replaced those and drained tank and put 10 gallons of fresh fuel in. Truck ran great for three days the. Started loosing throttle I put driving down the road and injection timing. Tried a known good pmd and same issues. Just installed a reman pump and NEW pmd from D-Tech. Also while it was apart, I removed the vacuum pump and I stalled a shorter belt. Built a spring style wastegate and put the pmd on a heat sink on the firewall above the hydroboost. Truck ran and drove great for 4 days and starts missing out right before lock-up and under heavy throttle in 3rd.

So any way to get rid of CEL from wastegate solenoid?

Any clue to what could cause the cutting out? My data from Tech2 looks great, I real signs of anything.

I have not checked fuel pressure yet or changed the fuel filter. I did pull the filter and it appeared new.
 
Cool, I'll watch that on the Tech2 tomorrow. Most oil pressure senders I replaced leak through the electrical connector and this one was fine when I replace the pump. Also I should have stated it doesn't throw any codes except the wastegate solenoid which is MIA. Know how to get rid of that code?
 
RyanH said:
If the oil pressure sender is bad the lift pump will shut off
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This is only true for 95-, 96+ OBD2 trucks use the ECM to trigger the fuel pump relay to run the fuel pump. The oil pressure switch is only there as a backup for OBD2 trucks. Get a fuel pressure guage on it and also you may want to put a piece of clear hose inline to watch for bubbles.
 
I don't believe a scanner will "see" the LP. It is activated by a 2nd set of contacts in the OPS.

You can jumper the connector; use a pressure gauge as previously stated.

A recommended mod is to install a relay to take the load off the OPS. Use the OPS only to activate the relay and wire the load through the relay.
 
The scanner will show if the lift pump is commanded on or off. From what I can tell, there is a relay for the lift pump in the relay box, and I have no clue to what a OPS is.
 
prichmon said:
I don't believe a scanner will "see" the LP. It is activated by a 2nd set of contacts in the OPS.

You can jumper the connector; use a pressure gauge as previously stated.

A recommended mod is to install a relay to take the load off the OPS. Use the OPS only to activate the relay and wire the load through the relay.
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Your thinking OBD1 95 and older trucks, 96+ OBD2 trucks activate the lift pump via an ECM triggerred by the ECM. The OPS mod to add in a relay is a waste of time and money on a 96+ truck since it is already done fro mthe factory(GM realized they screwed up on the 94-95 trucks and fixed it in 96).
 
Finally got around to test fuel pressure. At idle its 5-6psi and the slightest rev will drop I to 4psi. My source says 4psi minimum.

What should pressure be and what's a good pump?
 
So for anyone who reads up on this, we hooked a fuel pressure gauge up and got 3-5psi while idleing in the driveway and any little bit of throttle it would drop to zero untill cruising speed then sit at 2psi. Did some research and installed a AC Delco Fuel Pump part #EP1000, stated to be 12psi. I installed it today and checked fuel pressure and it was reading 8-9psi, then accadentally dropped gauge and broke it. Ran to town to pick up a 15psi gauge(100psi old gauge) and stopped to fill up on fuel and noticed when removing fuel cap the tank pops real loud and releases vacume.
 
Headcase98002 said:
So for anyone who reads up on this, we hooked a fuel pressure gauge up and got 3-5psi while idleing in the driveway and any little bit of throttle it would drop to zero untill cruising speed then sit at 2psi. Did some research and installed a AC Delco Fuel Pump part #EP1000, stated to be 12psi. I installed it today and checked fuel pressure and it was reading 8-9psi, then accadentally dropped gauge and broke it. Ran to town to pick up a 15psi gauge(100psi old gauge) and stopped to fill up on fuel and noticed when removing fuel cap the tank pops real loud and releases vacume.
Click to expand...

Sounds like somebody put a gas fuel cap on instead of a diesel one. The diesel caps allow air in, but not out while the gas caps will allow pressure to bleed off at about 2 psi but not allow air in. This is a common problem that peopel run into on trucks that run good for awhile, and then fall flat on ther face after about an hour of driving. Most aftermarket caps are made for gas even if you ask for a diesel cap, so make sure it allows air into the tank when you get a replacement.
 
The first time I checked pressure with old pump, I checked it at inlet of IP. Then I switched fuel pumps and checked it at the valve.

Ordering a GM cap today.
 
I'm having some more issues, if you all could help. When the truck gets hot, it start loosing power, surging and dies randomly. According to the fuel pressure gauge, it looses fuel pressure and the relay is farely hot.
 
Do you have the remote mount kit for the PMD? I have seen when those start to bad because of the heat. Check that and maybe swap in a new relay and see if that helps
 
If it's losing fuel pressure, you need to fix that first. Since you say the relay gets hot replace it first. Theres a good chance your lift pump could be going out and taking the relay out with it from excess current draw. Without proper fuel pressure the DS4 pump isn't going to work properly. Start with the basics and then go into the other stuff, but you gotta have at least 3-4 psi of fuel pressure to the pump for it to run correctly(5-8 is preffered though).
 
It's already had 2 lift pumps installed within the last 2 months. Just thinking it may have been a faulty part. New relay I stalled 2 weeks ago. The PMD is on the firewall near brake booster. New injection pump and new PMD by D-Tech.
 
If you have a new pump and relay, yet are still losing fuel pressure, then the dreaded fuel tank liner problem may be plaging you. GM used a plastic type coating on teh inside of teh tank, and in the last 4-5 years with ULSD it seems we are seeing alot of problems with the coating coming off and plugging up the tank sock on the fuel pickup. Most are dropping the tank, cleaning them out, removing the sock, and putting an inline filter before the pump.
 
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