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Lift Pump Problem - OPS or relay?

Thanks, thats great Doug, that has most of the info but I think we may also need a schematic for the Glow Plug Control System. Then we can tie both systems together and how they might effect each other. I have a basic schematic for the Glow Plug Control System from a Haynes repair manual but it has no color coding of the wires.
 
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It shows on the first diagram what the purple/white wire go too. It says "Hot in Crank" or something like that. Its towards the top on the leftish side.

I just posted the GP system as well though and the GP controller gets that same purple/white wire, #806
 
Thanks, I can zoom in and see the ppl/wht along the top now.

And the GP diagram I cannot read, which GP controller contact does the ppl/wht wire come off of?

I wonder if when people serviced the 93s they just removed that wire or forgot it, and I wonder why GM removed it in 94. I think I'll put it back in there.
 
OOPS sorry, I forgot to expand the photo before I copiedthe link to it to post here.

Also, all these photos I have posted are on my site which is www.mobileaudioguy.com/photos. The ones posted here are in the "I need help" section at the bottom.

The purple/white wire also goes to crank just like the LP relay from what I can gather.
 
Thanks again Doug. I think I have found the problem with my truck I'm not getting any power from the glow plug controller pin B during the wait to start cycle. Pin B is suppost to power the solinoid in the fuel pump relay, which will then fire up the fuel pump.

The glow plug controller I have on the truck is a fairly new Niehoff RL78051 (checked to make sure it is right one)and hasn't powered the fuel pump relay since new, I still have a Camdec corp controller that I switched out the original controller for in 1998. I switched out the Camdec controller for Niehoff because the wait to start time was getting to short, I just tested it, it also does not opperating the fuel pump relay(can't ever remember it running the fuel pump as well). I'm a little suspect of these cheap after market controllers, perhaps no internals to run fuel pump relay during the wait to start cycle.

I think I will either put in a new AC Delco glow plug controller or run a jumper wire from the glow plug output post to the fuel pump relay, I would need to put in a fuse and diode so that when the ignition is in start position it couldn't back feed to the glow plugs.

What do you guys think, any reason this wouldn't work?
 
tracy said:
Thanks again Doug. I think I have found the problem with my truck I'm not getting any power from the glow plug controller pin B during the wait to start cycle. Pin B is suppost to power the solinoid in the fuel pump relay, which will then fire up the fuel pump.

The glow plug controller I have on the truck is a fairly new Niehoff RL78051 (checked to make sure it is right one)and hasn't powered the fuel pump relay since new, I still have a Camdec corp controller that I switched out the original controller for in 1998. I switched out the Camdec controller for Niehoff because the wait to start time was getting to short, I just tested it, it also does not opperating the fuel pump relay(can't ever remember it running the fuel pump as well). I'm a little suspect of these cheap after market controllers, perhaps no internals to run fuel pump relay during the wait to start cycle.

I think I will either put in a new AC Delco glow plug controller or run a jumper wire from the glow plug output post to the fuel pump relay, I would need to put in a fuse and diode so that when the ignition is in start position it couldn't back feed to the glow plugs.

What do you guys think, any reason this wouldn't work?
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I highlighted it in red what im replying too. I did what the diode thing and it works great. I didnt have my camera that day so I wasnt able to take pics but I will take pics tomorrow or tuesday and post them.

As a newbie, im glad I could help. Everyone has been a huge help to me and the alldata was also a huge lifesaver.
 
Hi guys,
I scanned my FSM for the '93 models today, i'll attach the set for the auto tranny, let me know if you need the set for the manual. It appears that the lift pump is powered through the purple/white stripe wire when the starter is engauged? The OPS when the starter is not engauged. I thought the lift pump was powered same as the glow's. The same purple/white stripe wire goes to both, but it's from the starter. Hope these help.
Don
 

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It appears that the purple/white wire also goes to the B terminal of the glow plug controller it tee's in with the ignition switch in the start position. That's if I'm reading thinks correctly, it's been a few years since I've needed to read electrcal schematics. This thread has turned out to be a real bonanza for info and schematics.
 
tracy said:
It appears that the purple/white wire also goes to the B terminal of the glow plug controller it tee's in with the ignition switch in the start position. That's if I'm reading thinks correctly, it's been a few years since I've needed to read electrcal schematics. This thread has turned out to be a real bonanza for info and schematics.
Click to expand...

That is how I read the purple/white wire as well.
 
JMJNet that is just for the failing OPS problem, not the "LP not powered during WTS" problem.

In 94 they took the LP powered during WTS away, and I dont know why, I am going to put it back in. I'll test to see if the B terminal on the GP controller even activates with the controller. If not Ill rig another relay in or something.
 
You can hook up the above relay NC position to an ign "on" fuse like the F-SOL fuse to turn on the LP during start up until the OPS takes over.

My dad did the GP connection at one time, then the LP will turn on but only during the GP light which in a hotter climate like you, it will be only 2 to 5 sec. still not enough to prime the LP. He puts it back.

Just a thought.
 
i have a 95 6.5 turbo diesel and have changed the ops and the fuel pump relay but still get no power to my lift pump any ideas as to what route to go next would be of great help this is my first diesel have had for about 1yr now and dont think the lift pump has been pumping since ive owned it so i would really like to get this solved before it causes the more expensive injection pump to go out any help would be greatly appreciated
 
No i havent checked the fuse but will try and research were this fuse location is at and change that next. will the voltage going to the lift pump plug be sufficient to light a 12 volt test light?
 
Yes, it can show 12v on a light, but cucuit may not carry a load. I had a fuse connector only hanging together by 1 or 2 strands of the wire. It would light a test light, but not turn a pump on.

LP fuse is on firewall under cover on pass side.
 
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