Well guys, first time posting on this forum. I am an Ag mechanic but not diesel specific stuff. This one has me stumped and its my own truck!

Anyways, when I parked the truck it ran great and fine, no problems. Jumped in it this morning and she cranked and cranked but would not fire. Fuel pressure guage showed 12 psi, but goes down to about 5 while cranking, not sure if this is normal. Checked all the fuses... swapped some relays tried again, nothing. Disconnected the harness from back of the injection pump module, connections looked good. Disconnected the harness from throttle position sensor... looked good. Tried starting, nothing. Cracked 5 of the lines to the injectors, it would actually spurt fuel out, tighten them up, nothing. But here's the deal, when I disconnect the harness from the IP, and then crank the engine, it spurts the same amount of fuel! Maybe thats normal when the line is not hooked to the injector, Im not sure! In the process of messing around and cranking a lot, it actually did fire a few times but would never keep running. Do any of you guys have wiring diagrams for the plug going into the IP module? I just want to test for the basics going into the module, try to rule out a bad pump or module. One thing I forgot to mention was that I hear a "hiss" almost like a head gasket leak or something every time one of the cylinders come up on compression. I didnt think I heard it untill I started cracking injector lines! But then when I tightened them all the hiss was still there. I wonder if this is somehow related to my problem? I'm having a hard time pinpointing where the hiss is coming from.

Any info would be appreciated, thanks guys!

 

start it with eather,see how it runs,could be a air leak in lift pump lines

 

Did you get any codes?
Do you have vehicle theft alarm?

 

Well now just checked, I did get code P 1688, funny it only causes the check engine light to come on for a couple seconds and then goes away, but the code was stored there. But when I first checked for codes when it first was a problem it had nothing stored at all.

 

This is what I came up with from Chrysler tech support for your code, hope this helps you out.
Recommendation Clear the fault code, turn the ignition key OFF for at least 60 seconds, then turn the key ON (RUN position). Without starting or cranking the engine, check if P1688 resets. If P1688 resets at key ON, replace the injection pump. If the fault only resets with the ENGINE RUNNING, look for a loose power or ground connection to the injection pump (e.g. loose pin connections at the Fuel Pump Control Module 9-way connector, pin #6 and #7), or a bad fuel pump relay.
Load test the injection pump power and ground at the injection pump connector using a head light as a load.
Before replacing the injection pump, perform the following procedures. Test for a faulty injection pump... Bleed high pressure lines using the procedure in BR/BE service manual and see if engine starts. If engine starts, disconnect the lift pump and check if the engine starting improves. On a no start, after the lift pump stops running, the fuel supply pressure should drop rapidly back to -0- psi. With a hard start or no start concern, fuel pressure takes a long time (10+ seconds) to drop back to -0- psi. The fuel pressure may drop down in 'steps'. These symptoms indicate an internal injection pump problem. If the engine starts better with the lift pump disconnected, replace the injection pump. Another way to check for a faulty injection pump is to use the essential tool #3163834. The tool connects to the fuel injection pump module and isolates the problem to either the pump or to the ECM and wiring harness. Connect the tool's battery clamps to the negative and positive terminals on the battery. If the vehicle still will not start with the tool connected, you will need to replace the fuel injection pump. If the engine does start, the injection pump can be checked further by using the idle button to change between low and high idle speeds. If the engine does not respond, replace the injection pump. If the engine starts and changes idle appropriately with the tool connected, the injection pump is probably okay.

 

Fuel Injection Pump (diesel) - 9 Way Cav Circuit Function
1 K240 20lg/pk Data Link (-) Fuel Injection Pump
2 K242 20yl/pk Data Link (+) Fuel Injection Pump
3 - -
4 K44 18vt/or Camshaft Position Sensor Signal
5 K45 18lb/rd Knock Sensor Return
6 Z12 14bk/tn Ground
7 A40 14rd/lg Fuel Pump Relay Output
8 K48 18dg Fault Signal
9 - -

 

Did you replace fuel pump relay in pdc or swap with another relay?

 

Wow, thanks for all the help BigIron! I did swap that fuel pump relay with another relay a couple times, no difference. I also DID notice that with the key on when I pull out and insert the relay I hear a click from that relay PLUS the injection pump! Not sure if in the pump whether its a click in the module itself or if its something inside the pump clicking. I think thats a good indication that the pump is getting power and ground, and from my understanding from what I read, the pump only needs power and ground in order for the engine to start. Also I went through your procedure above... I cleared the code out, checked to verify the code was gone, then turned off the key for more than 60 seconds, then turned the key back on and the P1688 code was back... so Im pretty well guessing the pump is toast. The only thing I cant explain is why the engine fire randomly here or there. Its not like it tries to fire every time I crank it, but just happens 1 out of every few continuous tries to start it.

 

Chrysler tech support would always required me to load test the power circuit to injection pump first before the injection pump was replaced. I have a jumper box that plugs into injection pump. This eliminates all wiring and ecm from circuit so injection pump failure can be confirmed. I would load test the circuit with headlight first before I replaced injection pump.