Injection Pump troubleshooting

[ak diesel driver]

the ops and crank sensor kinda work together but seperately. in order for it not to run both would have to fail. Just so there is no confusion tell us exactly is happing with the LP and fuel pressure. If your getting pressure how many psi or measure the volume by filling a jug and timing it. 94-95 are very particular when it comes to the ops/lp system working properly.

 

[mgray]

For what it's worth, my last LP that I replaced would still run my truck, but not give fuel out t-valve. New LP pisses hard out t-valve.

I'm no expert but I think IP is your issue

 

[ak diesel driver]

while it very well could be IP it would really suck to change the IP and still have issues.

 

[GTOJohn]

the ops and crank sensor kinda work together but seperately. in order for it not to run both would have to fail. Just so there is no confusion tell us exactly is happing with the LP and fuel pressure. If your getting pressure how many psi or measure the volume by filling a jug and timing it. 94-95 are very particular when it comes to the ops/lp system working properly.

Will check it tomorrow. I have a fuel pressure gauge, where is the easiest place to check it? I don't remember seeing a schrader valve anywhere.

For what it's worth, my last LP that I replaced would still run my truck, but not give fuel out t-valve. New LP pisses hard out t-valve.

I'm no expert but I think IP is your issue

I have a gut feeling of that too, mgray. $$ are flashing before my eyes...

while it very well could be IP it would really suck to change the IP and still have issues.

No kidding, ak. I almost don't mind putting the money out for the pump IF it fixes the problem.

Thanks for the help, guys...

John

 

[ak diesel driver]

Kind of a pain to do but I would pull the hose from the FFM to the Tvalve and verify it isn't plugged. The tvalve is the easiest place to hook up a test guage. the bleeder valve on the filter usually leaks like crazy.

 

[GTOJohn]

Thanks ak... I already pulled and blew out this line, so I know that it isn't plugged. I will pull it off at the T-valve and check the pressure there.

Thanks,
John

 

[buddy]

Just to be clear, you are opening the T valve several turns when checking for fuel? You need to turn it like 5 or 6 times to open it up, it is like a needle valve.

Also to clarify, the OS and the CPS work together to provide timing to the PCM. The OPS only runs the LP, but dont even be concerned with the OPS at this point, it only matters after the truck is running. While cranking the LP is powered by the LP relay, a separate parallel power source only when the ignition is in the start position. You dont have to crank to get the LP to run, you can put the truck in gear then turn ignition to start, it wont crank but will run the LP.

I assume that the truck still won't start even with the new PMD. First thing I would do is pull the fuel inlet off the IP and make sure fuel is coming out there. Are you sure there are no stored codes? Did the SES light flash 12 repeatedly when you jumpered A and B on the OBD1 port? Or maybe 13? Make sure you have voltage with the ignition to the PMD and the Fuel/Engine Shutoff Solenoid (tall cylinder sticking up) on the IP. If you want to eliminate the ESO solenoid on the IP as a possibility you can unplug it and spin it off, with a snap ring pliers you can remove the snap ring holding the plunger in and it will fall out. Then the plunger cannot stop fuel from reaching the injectors if it ever was.

If you know how to use a multimeter and read this thread, I explained how to test if the IP is actually getting the right injection signal. http://www.thetruckstop.us/forum/showthread.php?23904-jump-A-B-13-not-12-Poppet-Valve-IP-Question

This person eventially came to realize he had some bent or broken pins in the PMD cabling connections that was preventing him from getting the proper signal to the IP's fuel solenoid. Another possibility is that the fuel solenoid harness is broken at the IP under the rubber boot. You should be able to test continuity on the PMD harness across the fuel solenoid and get a low resistance reading through its coil. All the needed info is in the above referenced thread.

 

[ak diesel driver]

I reread my post and realized I'd put OPS instead of OS. Thanks for catching that Buddy. Darn acronyms

 

[GTOJohn]

Thanks guys... So where is the OS and is there a way for me to troubleshoot it? I doublechecked and I only have code 12, which I assume to be no stored codes. That is a great thread, buddy!

 

[buddy]

You should try unplugging the OS to see if it starts, it is on top of the IP. A dual row connector you can get your fingers on just enough.

There is the stuff in the post mentioned above. There is not much to troubleshoot the OS other than unplugging it. It would normally code if it was bad even with just cranking. If you want to know more about OS maintenance you can go through this thread. http://www.thetruckstop.us/forum/sh...sel-engine-lost-power-doesn-t-do-over-2500rpm

He never updated the thread but Shellieman's truck is running "awesome" in his words since adjusting the OS per the instructions in the thread.

 

[GTOJohn]

I opened the T-valve fully open and had fuel coming out of the drain line in a steady stream. This is the first time that I have checked it after disconnecting and blowing out all of the hoses.

I verified that I had fuel coming out of the line going into the IP. I connected my fuel pressure gauge at that spot and found 7 PSIG. Is this correct pressure for the LP?

I unplugged the OS and I had the same results with and without it plugged in. I have one of the injector lines removed at the injector and have never seen a drop of fuel come out of it.

I didn't get a chance to check voltages or try to the ESO plunger trick.

Thanks again,
John

 

[ak diesel driver]

Starting to look grim

 

[buddy]

At this point most would assume the IP is dead. You can also try unplugging the CPS to see if that makes any difference. PCM only needs the OS or the CPS to start and run the truck. Although it will take about 10 seconds of cranking to get it to start in either case. In general you should crank for more than about 15 seconds and not more than once per minute.

I would check to make sure the IP is getting the proper injection signal though. That is the 1.2VAC on pin B output of the PMD. You dont have to tap into the Fuel Solenoid ground wire to check that, just VAC across pin B to any ground. Everything has to be connected and cranking to test that 1.2VAC, so you are looking at poking though the wire insulation or shaving a little off to get a meter to clip onto it.

But first with PMD unplugged and ignition off check the resistance through the IP fuel solenoid across PMD harness pins B and F, should be about 0.4ohms.

 

[GTOJohn]

Excellent. Thanks guys...

So, just thinking ahead. I don't want to spend $1k on an IP. Are the rebuilt units on ebay any good? I think they are about $300? Any other suggestions on a parts vendor?

John

 

[ak diesel driver]

I'm running a rebuilt from Pensecola was about $450. I've been hearing neg reports lately but mine was a good one.

 

[buddy]

On the cheap ones, what you may get is one that has 100,000 miles on everything and an OS failed, so they replace the OS. Or maybe just the PMD was dead and they put the IP back out there. And you have an IP that works but all the rotating parts or Fuel Solenoid still have 100,000 miles on it. Who knows how long any of those parts will last. I have even seen multiple cheap rebuild come with the OS out of calibration, as if it was replaced and not actually tested. That doesnt mean they wont work and a good amount probably last a really long time.