No power to lift pump

[Diabolic]

Forgive me for making this my first post. I found this board due to the troubles I am having.

1993 C2500 (Air Force) 6.2L Diesel 3/4 Ton

The truck was surging and sometimes spontaneously dying while driving. It would start back up and drive again. Sometimes the surging would go away, sometimes not. Changed the fuel (lift) pump and the filter. Now the truck will not start at all.

I checked voltage to the pump and got nothing, so I checked at the box where the gray wire that runs to the pump enters the box (forgive my ignorance but I don't know what the box mounted on the firewall is). Continuity but still no voltage when turning the key over. What else can I check or what is likely to be the problem? Checked all fuses, although there are a number of empty slots.

Any help is greatly appreciated!

 

[Acesneights1]

A 93 ?? Are you sure i's a 6.2 and not a 6.5TD ? Does the Engine have a Turbo ?

 

[just a number]

IIRC '93 was the last official year for the 6.2. did you happen to check the relay itself?

 

[Diabolic]

IIRC '93 was the last official year for the 6.2. did you happen to check the relay itself?

It's definitely a '93 and 6.2L Diesel.

If I am permitted a stupid question (I own a machine shop but I don't know cars): where is the relay located? I know how to check for power but I don't know what to check for power, beyond the pump connection.

 

[DieselCash]

The relay is located on the fire wall on the passanger side under the hood. There should be a nice cover on it that comes off with two or three large black hand screws. If I was at home I would snap a picture for you.

You having a 6.2 and not a 6.5TD, do you even have a lift pump on the frame rail(it is located under the drivers seat area) like the 6.5TD?

 

[Diabolic]

The relay is located on the fire wall on the passanger side under the hood. There should be a nice cover on it that comes off with two or three large black hand screws. If I was at home I would snap a picture for you.

You having a 6.2 and not a 6.5TD, do you even have a lift pump on the frame rail(it is located under the drivers seat area) like the 6.5TD?

Yes, the lift pump is bracketed to the frame, just under and slightly behind the driver's side door.

However, the wiring seems to run into a box on the firewall but on the driver's side. I took the cover off of the box and was greeted with a soldered circuit board. A bundle of wires runs out the back of this box, through the firewall, high near the top of the dash.

 

[Acesneights1]

Not sure one this one. Never seen it.All the 93's I have seen were 1st gen DB2 6.5TDs. Perhaps some pics ?

 

[Diabolic]

Ok, I found and replaced the fuel pump relay. Still no fuel pump action when I turn on the key. I have checked all fuses, replaced the pump, and replaced the relay. What else can it possibly be?

 

[just a number]

did you check for power at the relay? broken wire perhaps? don't forget to check the ground side too. everybody always jump to the live side but given the grounds record.........

 

[Acesneights1]

How are you testing for power at the LP ? I had a Dodge that drove me crazy and turned out to be bad batt connections thanks to the scumbags at Lee's Auto Ranch in CT. I would test at LP under load with a voltmeter.

 

[buddy]

The 1993 setup is mostly the same as the 94 setup setup. Just read the 6.5 OPS/LP sticky. I added OBD1 stuff like ours in later posts, so read through basic stuff on first page but realize the OBD2 setup is different and read my posts on the second page for info on how yours works.

http://www.thetruckstop.us/forum/sh...t-Pumps-amp-OPS-operation-and-troubleshooting

The pump runs off of the Oil Pressure Switch while running, you can check pin G of the diagnostic port while its idling to see if there is any voltage coming out of the OPS. Your LP should run during Glow Time and cranking from the relay and when the engine is running from the OPS, but otherwise not just with the ignition, except during glow.