Truck won't start (i searched)

[The Ru]

Hey guys, wanted to start off saying that i joined the forum to find info, and that i did. I've read about 100 threads, but im not sure i fall into a generic problem like most. Heres the story:

Bought the truck from my brother. 1994 Chevy 2500. 6.5 TD Has:
S/S PMD and Heatsink on manifold
S/S #9 resisitor
S/S cooling upgrade
S/S intake kit

I buy the truck, transfer it over (title, etc), bring it home. We (bro and I), go to do some matience. Bro goes to check fuel filter for water, cracks the bleeder and it dies. Never to restart. He leaves (was visiting from out of state). Im decent with cars and mechanics, but know nothing about diesel. So he tells me to (and i did, in order, not fixing the problem) replace the electic fuel pump (frame rail), OPS, Fuel Pump relay. I checked all fuses. (are there fuses in the engine bay somewhere as well?).

The truck just turns over, not trying to start at all. If i put it in D, and turn the key, i dont hear any fuel pump going on. And there isn't voltage (12 V) to the frame rail fuel pump when the key is on (should there be?).

I'm fearing an injector pump. What do you guys think? No Check Engine Codes that i saw.

Any help is really appreciated, as im getting annoyed with the dead truck in my driveway. Its going to a garage if i can't figure it out this week. I need it to haul my Trackbikes around!

Heres the MAT, that it has had. Its at 192k now.

165,000 new motor
169,500 new tires
169,500 new air filter system, glow plugs, #9 resistor
171,000 new fuel filter $15
171,500 Oil changed
174,400 Crank Case decompression valve $60
174,850 New PMD and cooler $500
178,028 changed fuel filter
178,200 oil and filter changed
180,300 Cleaned Air Filter
180.350 New Head Unit $500
180,400 New Marine Injectors $500
181,500 Cooling upgrade $560
181,600 New Starter
181.650 Fuel Filter
181,700 Rotate Tires, Oil Change, New Ac Pump, dryer $600
181,700 rear brakes lines n adjustment $650
186,891 Change Oil and filter, Changed fuel Filter, Cleaned Air Filter


Thanks

Ian

[byte]

hello... if you open the valve by the thermostat cover and the engine dies... that means the electric fuel pump (under the drivers side door by the frame) is dead--or the relays-oil pressure sender that feed it power... these trucks will actually run not too bad without these pumps working... until you get air into the system... you could run a long wire from the battery and hook to the inline fuel pump to see if it works or not...

the pump will not get power until the OPS senses oil pressure... check all the fuses with an ohm meter or fuse tester ( i got 1 free with a pack of fuses and it is sooooo handy... it is self powered and you don't have to pull the fuses)... YES there are the fuses under the hood by the brake booster...

[gmctd]

Welcome to the 'Page, Ian...........

There is a 20a fuse in a rubber holder over on the firewall above the turbo - may be behind that plastic cover over the power-block - check that, also the fusible link for the orange wire

[JohnC]

Open the bleeder on top of the filter. Have someone crank the engine while you watch the bleeder. Fuel should come out after a short while. you may have to crank it for several short intervals too avoid overheating the starter. Try cranking for 15 or so seconds then letting it rest for 2 minutes. If you don't get fuel after 3 or 4 tries, the pump is probably bad. If you do, close the bleeder and the engine should now start. At your earliest convenience, replace the oil pressure switch.

The '94 won't run the pump with the key on start and the shifter in drive.

[gmctd]

I thought he indicated he had already replaced those in order at his bro's insistence, which did not fix it?

[The Ru]

Okay guys, update. I got it running. There is no power to the electric fuel pump. What we did was jumper that pump to get it to run, and cranked it forever till it bled itself and started. So everything i replaced i really didnt have to replace.....DAMMIT! but at least i know its all new. That fuse next to the relay is good. And i did replace the OPS.

So where do i go from there? I guess i have to trace wires back. If i unplug the relay, there is 12V there(hot all the time), but when you turn the truck on it does not send it to the pump to turn it on. Its a new relay... I dunno what could be causing this but a broken wire...?

I have the wiring diagram here: (figure 15) http://www.autozone.com/az/cds/en_us/0900823d/80/08/79/51/0900823d80087951/repairInfoPages.htm

Its a bit confusing though.

Thanks for your help guys.

[byte]

my 1994 gm manual shows a inline fuse as well as a fuse in the fuse block ... either would cause no power...

fuse block--- CRK fuse 5 amp (crank?)

inline fuse--- 20 amp

either check the fuses with a ohm meter or replace... i have had a couple fuses that look just fine... but when tested they are burnt out somewhere that you can not see!

good luck... i could send pic of gm manual glow fuel circuit if needed....

[gmctd]

OBD1 energizes the LP in START only, then OPS takes over when engine is running and oil pressure comes up - '94 has a fusible link in the orange supply wire on that power block

[The Ru]

I'll take that fuel circuit diagram. thanks

nashoba@ptd.net

And i checked that orange fuseable link, that was good. I thoguht i got all the fuses but i will double check them.

thanks

ian

[JohnC]

My recollection is that power passes through the fuel pump relay under both circumstances. When the starter is engaged the relay pulls and power passes through the NO contacts to the lift pump. When the starter is off the relay drops out and power flows through the NC contacts to the OPS and then to the lift pump.

If you jumper from the hot pin on the relay socket to the NO pin the pump should run as it should when the starter is engaged. If it doesn't, the wiring to the pump is bad. Similarly, when the relay is off the (orange?) wire on the OPS should be hot and if you jump to the (gray?) wire the pump should run. (Confirm pins and wire colors before proceding! I am not liable for mistakes!)

The autozone diagram doesn't show the OPS. The red wire shown is in the ALDL connector under the dash. Put 12 volts on it and the pump should run. The OPS should compete the circuit from the red wire back to the fuel pump (gray wire). If I do not recall correctly then the OPS connects from the orange wire to the gray wire and the relay is not in the circuit when the starter is off.

[byte]

I'll take that fuel circuit diagram. thanks





there is an email waiting for you!

[The Ru]

there is an email waiting for you!

got it/ thanks.

ian

[The Ru]

So i finally got a chance to go at the truck with my Mulitmeter. I checked all the wire paths and they are all good.(From Fuel pump relay, to fuel pump, to OPS). Everything thats supposed to go where it should does. That said:

Still no power to the Lift pump itself. The truck runs without it. (remember i jumpered it to keep pressure to get it bleeded and started).

I didnt check the 'C' link off the fuel pump relay. It says on the diagram it goes to the 'DLC'? what is this and where can i find it?

'F' off the fuel pump relay goes to the fuse in the fuse panel labeld CRK. In the Diagram is says "hot in crank". With the truck running, there is no 12V on this like i would assume there should be. WHere does it go to/from?

Both the OPS and the Fuel Pump have wires that go to 'Instrument Cluster'. what are these for, and can they effect my problem?

thanks guys.

[gmctd]

OBD1 LP runs in START - pulls LP START relay in, closing fusible-linked hot circuit to LP - release START, relay opens, LP stops if engine is not running

If engine is running, oil pressure closes OPS, connecting hot circuit to LP

The red wire to the inst cluster goes to the ALDL connector pin G for testing - when the relay is off, normally open, you can put +12v on pin G to turn on the LP - when the engne and LP is running you can check for correct voltage level, indicating failing LP or OPS

There is a fusible link to the relay and OPS, and a 20a fuse in the LP circuit - there is a 5a CRK fuse in the courtesy center fuse panel for the relay coil - which is prolly good or you wouldn't get LP run in START

[The Ru]

OBD1 LP runs in START - pulls LP START relay in, closing fusible-linked hot circuit to LP - release START, relay opens, LP stops if engine is not running

If engine is running, oil pressure closes OPS, connecting hot circuit to LP

The red wire to the inst cluster goes to the ALDL connector pin G for testing - when the relay is off, normally open, you can put +12v on pin G to turn on the LP - when the engne and LP is running you can check for correct voltage level, indicating failing LP or OPS

There is a fusible link to the relay and OPS, and a 20a fuse in the LP circuit - there is a 5a CRK fuse in the courtesy center fuse panel for the relay coil - which is prolly good or you wouldn't get LP run in START

You'll have to help me a bit with acronyms. ALDL?

[DmaxMaverick]

You'll have to help me a bit with acronyms. ALDL?


Assembly Line Diagnostic Link

The connector under the dash for connecting an Tech I, Tech II, reader/scanner, or jumpering to read/reset DTC's (Diagnostic Trouble Codes). ALDL is associated with OBD I vehicles (prior to 1996). Later vehicles are OBD II, and the connector is generally called the diagnostic port, and they cannot be used in the same manner. OBD II cannot be used to pull codes with a paper clip, a Tech II or scanner/reader is required.

More info, the procedure for reading/reseting codes and a DTC list can be found HERE (http://www.thedieselpage.com/members/trblcode.htm).

[The Ru]

gotcha. Im pretty familar with cars, electronics, etc. I'm not with domestic anything though.

I do BMW, Subaru, and Metric Sport bikes. This would be my first foray into working domestic trucks...lol


But i use it to haul our track bikes around though!

thanks

ian

[The Ru]

Alright guys. I went back at it over the weekend. I have 12 on the fuse for the starting LP power, and when running i have 12 V to the pump and its working. SO i guess it was one of those things i replaced. Not sure how i missed it before, but its working now.

Thanks for all the help.

ian

[tommac95]

I dunno model year '94.... You write:
>There is no power to the electric fuel pump.
If this was determined by checking the voltage between the two wires supposed to feed power to the LiftPump (LP) , there exists the possibility that there may be no ground continuity {on '95 the LP grounds thru the engine harness at rear psgr side head , but who knows on '94??} , that is , a break in the wire from the connector to the ground terminal. So may want check voltage between known ground and the 'hot' (+) wire/lead at the connector. Technically could look for voltage drop from battery terminals to the + and (-) LP connector terminals. (If you had found no voltage from a frame-grounded test lamp, then your conclusion is well-founded ; ignore above).
--Not to blow smoke ; just suggest proceed methodically when discover anomalies.

Particularly on '95, many had good results from ignition switch replacement....These can cause intermittent functions of some components on the ignition circuit.
T m