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lift pump issues

C

croberts

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Location
Richwood, Ohio.USA....smalltown, USA
I'm glad I found this site there is alot of good info from people who know these 6.5 TD.. I have a 95 6.5 and have hot start problems. It will start and run for about 20 seconds then die. I rep[laced the IP ( about 1,000 miles ago) and a dealer replaced the OPS a few years ago when I had my first go around with the PMD. Since the dealer replaced the PMD and the OPS i have since relocated and replaced the pmd to the top of the intake on a heat sync. I thought the new pmd and injection pump would take of it, but it did not. I am now back to the lift pump since reading how to open the tee to check for fuel while engine is running... I got no fuel out the tee and the engine died. With the truck running I get voltage at the lift pump ( with a test light ) seems ok, but no fuel at the tee with truck running. To get by i have been pulling the fuel pump relay on the fuse block under the hood drivers side and jumping pin 30 to pin 87 and i can get it running and be ok unless I need alot of throttle then it spit and sputter a few times and recover after i let of the pedal a minute. When i jumper pin 30 and pin 87 ( LP sounds good and strong ) and start the truck I can open the tee and get a good stream of fuel without stalling the engine, this tells me the Lift pump is ok. But I am confused why undr normal operating conditions I have power ( with test light at LP ) but no fuel at tee and killing the engine. What is the relay i am jumping used for? Is the ground on a switch or relay? Is the voltage regulated to the LP by something or is it either on or off? this is a LP i got at NAPA and spec'ed for this truck.... Sorry to ramble on but I am really frustrated, trying to get the crops out of the field and have to let the truck run all day so dad will not have to mess with it. Thanks in advance for any help !!!!!!
 
Sounds like the OPS packed it in again
the relay only powers the LP with the key in crank mode,after start the OPS takes over running the LP. One of the 2 paralel terminals of the OPS connector is always hot,the other one powers the LP after oil press is build. the offset terminal is for the Oil press gauge.

LP ground is on rear dr side head.
 
"i have since relocated and replaced the pmd to the top of the intake on a heat sync."

The first thing I would do is get this out of the engine bay or you will be needing another one.

Next I would get a fuel gauge on it to see if the pressure is right. If your getting good flow steady with the relay jumped but not when it has the relay in you might have a bad relay (engine cranking) Is the OPS a Delco? May also be a bad one.

Run fuel into a glass jar for a minute or more is there any bubbles?

Last is, your sock in the tank might be plugged and your not getting the volume of fuel or your fuel filter might be plugged.
 
As the contacts get fried in the opsu it will show power at the lift pump but won't have any amperage to actually run the pump.
 
x4, definitely the OPS. The OPS controls the LP when running and it can have the correct voltage but not passing the correct amp. OPS is the weak point in the system, a few years is a lot for one of this. Get an ACDelco OPS which will behave correctly compare to the aftermarket.

If I were you, I would go further by adding the relay. There is a link from the Tech Library part of OPS section.
 
Thanks everyone !!! The relay was bad has been replaced. LP will run when the truck is in drive and turn the key to start...great , one problem fixed ..still no fuel at tee with truck running ...... I will pick up an ops switch today after work and install this weekend... thanks again and will post update later.
 
By the way I dropped the tank last summer and relpaced the sending unit and all new fuel lines up to the LP. Not seeing any bubbles in the fuel ... will take a closer look this weekend. Where is the best location for the pmd when I get a chance to move it I will..and where to get a good but cheap extension wiring harness for it?
 
Replaced the OPS and the truck is running and starting great. The fact that I was seeing voltage at the LP but not the correct amperage ( i was not measuring amperage ) due to the faulty OPS was really throwing me off. Thanks again to all of you for replying and providing details to me so that I could understand what I was seeing. Now I can feel good about this truck again and start to make improvements to it. I will probably replace the injectors and glow plugs next. I'll look for threads here related to these items on this site. Oh yea a new mufller and exhaust pipe first probably . Flowmaster, magnaflow? I want a nice sound ( not too loud ) with no power loss and improved fuel mileage what should I look at ... again thanks alot guys !!!
 
Glad to see it's running good for you again. Another site vendor to look at is Heath diesel he has a great selection of parts for our 6.5s and is VERY knowledgeable about them and just happens to have the fastest one on the planet!!!!:eek:

http://www.heathdiesel.com/
 
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