Archived Truck only runs for 10-30 seconds.

[Nschroeder]

I would also like to add that whatever is shutting the engine down is also cutting the lift pump also. The engine cuts first then the fuel pressure drops about half a second later. Trying to crank after shutdown the fuel pump will not run and the wait to start light will not cycle. When I unhook the batteries and try again everything works as normal, for about 3 seconds after startup.

Thanks for all the good ideas, I would love for this to be a simple stupid problem that got by me and would be cheap to fix.

Nick

 

[JLandry]

I would also like to add that whatever is shutting the engine down is also cutting the lift pump also.

I'll keep giving it some thought and let you know if I come up with any more ideas, but at this point I'm leaning toward the ECM. They do occasionally go bad.



John L.

 

[Nschroeder]

I cant thank you guys enough for all the time you have spent working through this. I have learned a great deal about the electrical system on my truck that will for sure help me in the future. I should have a different ecm here monday afternoon or tuesday to try and see what happens.

Thanks again

Nick

 

[Sticks]

Are you still getting the same codes?

 

[Nschroeder]

The truck is not throwing any codes unless I cause them by hotwiring the pump.

Thanks

Nick

 

[Nschroeder]

Replaced the ecm and there was not really any change. Got code 1688 and 1689 to pop up twice but the last few attempts no codes have come up.



It seems now like after the truck starts the voltage to the vp slowly starts to drop until around 10. 5v at which point the engine shuts down. It seems to be a steady slow drop.

 

[Sticks]

P1688 Internal Fuel Injection Pump Controller Failure

P1689 No Communication Between ECM & Injection Pump Module

OK, those are the two codes that you need to have a trouble shooting tree for, and you do need to run both. You might get lucky and get a dealer to give them to you. Hopefully someone on line here can send them to you. I no longer have access to All Data.

 

[JLandry]

Replaced the ecm and there was not really any change. Got code 1688 and 1689 to pop up twice but the last few attempts no codes have come up.



It seems now like after the truck starts the voltage to the vp slowly starts to drop until around 10. 5v at which point the engine shuts down. It seems to be a steady slow drop.

Nick,



This doesn't sound right. Power to the VP44 comes almost directly from the battery through a 20A fuse and relay. There's nothing that should cause the voltage to slowly decrease before it cuts off completely.



Where are you measuring this voltage?



Could you possibly have weak or nearly dead batteries, and when the intake air heaters are kicking on, they're dragging down the entire system voltage enough to where the ECM is shutting off? The ECM does have a minimum voltage requirement to operate. If the ECM shuts off it will cause the VP44 power relay to turn off also.



Can you hook up jumper cables to your truck from another strong vehicle to see if this changes anything? Or at least charge your batteries for a day or two?



John L.

 

[JLandry]

P1688 Internal Fuel Injection Pump Controller Failure



P1689 No Communication Between ECM & Injection Pump Module



OK, those are the two codes that you need to have a trouble shooting tree for, and you do need to run both. You might get lucky and get a dealer to give them to you. Hopefully someone on line here can send them to you. I no longer have access to All Data.

These DTC's could have been present in the ECM from repairs or reprogramming. If you erased them and they don't come back, then you can safely ignore them.



Just in case, I've attached the diagnostic procedures for the P1689 DTC.



For the P1688 DTC, there's really nothing to troubleshoot. If that one repeatedly comes back, you simply replace the VP44.



John L.

 

[Nschroeder]

Well this is interesting, I swiched the batteries out to a pair of known good batteries with no change. I check the resistance from the pdc to the vp44 on both the hot and ground wires and could not find a problem with the wiring. So i guess I will pull the wires out of the loom and try to find a break or rub somewhere again. It is strange how the voltage counts down almost with a purpose after the truck starts however a second meter on the battery shows 14+ volts before the truck shuts down.

Thanks for the help

Nick

 

[Nschroeder]

I forgot to say that I am measuring the voltage right before the vp on the wire I soldered onto the pump wire for testing purposes.

Nick

 

[JLandry]

I forgot to say that I am measuring the voltage right before the vp on the wire I soldered onto the pump wire for testing purposes.

Nick

Nick,



Is this tap you made on the 14 gauge Red wire with a Lt. Green stripe near the VP44 connector?



Thanks,



John L.

 

[JLandry]

I check the resistance from the pdc to the vp44 on both the hot and ground wires and could not find a problem with the wiring.

Nick,



Another idea might be to measure the voltage being supplied to the ECM before and immediately after starting the engine. I'm wondering if possible there's something wrong with the ignition switch circuit that could be cutting off power to the ECM, which would in turn cut off power to the VP44 through the fuel pump relay in the PDC.



Pin 5 of the ECM has an 18 ga. Lt. Green / Black wire which should have battery voltage present when the ignition is in either the RUN or START position.



Pins 48 and 50 of the ECM both have an 18 ga. Red / White wire that should have battery voltage present at all times.



John L.

 

[Nschroeder]

while the truck is running there is only 8v being supplied to the fuel pump relay should there be 12v there?

 

[JLandry]

while the truck is running there is only 8v being supplied to the fuel pump relay should there be 12v there?

Nick,



I’m pretty sure it should be battery voltage (above 12 volts), BUT i'm always willing to be proven wrong!



According to the P1689 diagnostic procedure I posted earlier, with the engine off and the VP44 wiring harness disconnected, you should measure AT LEAST 8 volts on the OUTPUT side of the Fuel Injection Pump relay. That would be pin 87 on the relay and is the 14 ga. Red/Lt. Green wire running between the PDC and the VP44. Below 8 volts I don't think the either ECM or VP44 will operate. If you're only seeing 8 volts with the engine running, then you're running right on the ragged edge and it's no wonder the engine is shutting down.



If you're still measuring a full 14 volts at the battery and only 8 volts at the VP44, then I would guess something is definitely wrong somewhere in either the wiring or the charging system.



John L.

 

[Nschroeder]

I am getting the full 14 volts to the vp44. I will try to explain this the best that I can. Measuring the relay trigger wire the wire from the ecm that triggers the fuel pump relay. When the key is turned on the wire will have batt voltage. as long as the lift pump continues to run this wire will have 14 volts.



If I hot wire the pump the lift pump will only run for about a second after I stop cranking and when the lift pump stops the trigger wire from the ecm to the fuel pump relay drops to 9 volts with the new ecm or 7 volts with the old ecm. The truck seems to exibit much the same symptoms with either ecm. the truck is randomly popping about any fuel pump controller code that you can think of the most common one being p1689.



If the pump is not hot wired the truck shuts down about the same time as the lift pump I would say that the lift pump runs slightly maybe half a second longer than the truck.



I also tapped into the ignition wire feeding the ecm this wire maintains batt voltage whenever the key is on no matter what I do. I believe it was pin 5 on the ecm.



Now if i just hot wire the pump with the vp44 harness unplugged completly the truck starts and idles good. If i use my modded harness to supply batt voltage while the harness is plugged in the truck will kind of run but it catches and misses alot and smokes the shop up with white smoke in just a min or so.



Chip fisher has offered to send me a new vp44 and said he would buy it back if that was not the trouble so that might be my next move unless someone has an idea about the relay trigger wire dropping voltage.

Thanks and I hope this is helpfull

Nick

 

[JLandry]

Nick,



I understand the wire you're describing.



Based on the fact that both the original and replacement ECM's are behaving in a similar manner, at this point I'm leaning toward thinking there's nothing wrong with either.



Can you measure the voltage on the 18 ga. Lt. Blue/Red wire running between pin 33 of the ECM connector and pin 5 of the VP44 connector? This is the Fuel Shutoff signal line. It should have NO voltage at all times whether the engine is running or not. If you measure voltage here, then that'll tell us the ECM is asking the VP44 to shut down because it's detecting a problem somewhere.



Also, have you had the chance to measure the voltage present on pins 48 and 50 of the ECM I mentioned in message #33? Both have an 18 ga. Red / White wire that should have battery voltage present at all times.



I'm beginning to wonder if the ECM is shutting down the VP44 on purpose in response to some problem input.



John L.

 

[Nschroeder]

The fuel shutoff wire never has any voltage except for a couple seconds after the key is turned off which as I understand is how its supposed to operate. Both pins 48 and 50 on the ecm have battery voltage supplied to them all the time. I was talking to chip fisher again today and he said that between this and one other truck he is rethinking the open loop closed loop system switch location and thinks that it is actually on the vp44 not in the ecm. So he thinks that that being the case then there could still be a problem with the vp44 module not communicating with the can bus causing this issue.



I got onto alldata and followed all the trouble trees for every code that came up and some pointed to the vp and some pointed to the ecm. The only thing that is odd that I can find is the voltage dropping to the fuel pump relay and the lift pump shutting down. when this happens the wait to start light also will not function until the batteries are reset.



I cant think of what would be telling the engine to shut down or what even has the authority to accomplish that. The only thing I can think of is does the pcm have any ability to tell the ecm to kill power?

Thanks

Nick

 

[Sticks]

When you say that you have run the trouble trees, did you just follow the steps?

Example.

Step 3: Check the resistance on PCM pin 48 to VP44 pin 7. If resistance is below 1 ohm, skip to step 7.

Step 4: Check resistance on PCM pin 48 to all other pins on VP44. If continuity exists, inspect harness for short to other wires.

So you did step 3 and it was below 1 ohm, so you skipped to step 7. Steps 4, 5, and 6 may show something wrong.

What I am getting at is occasionally you have to do every single step the tree calls for. Sometimes things do show up. Especially when testing harnesses that are disconnected and pulled back away from where they are normally sitting. This can cause a break in a bad wire to no be broken anymore.

Voltage through a high resistance wire will cause heat, which causes expansion. An 18 ga wire with only 1 of 12 strands still in one piece will show good continuity, but will not carry any load. Not sure how to do a voltage drop test on something like this when the conditions change so rapidly.

Also when testing harnesses, if you can get your meter leads to stay connected, try moving the harness or massaging it while you are testing it, it may help find that weird brake.

 

[Nschroeder]

Well I believe I may have found the problem today. I was getting intake tubes out of the way to get at the vp for removal and the pump wire tap looked funny. On closer inspection the pump wire itself had broken and was sitting at a funny angle but still touching. I fixed the connection and am currently in the process of putting everything back together to take it down the road and see what happens.

Thanks

Nick