‘94 stalling with new PMD

[Big T]

’94 continues to have stalling problems after replacing the PMD which is mounted in the bumper. After a stall it will restart after about 10 seconds of cranking. “That's with turning the key on cranking 5 seconds turning the key off cranking and boom we have ignition.”

 

[jrsavoie]

Do you have a fuel pressure gauge?

Is it always the same or does it start right up sometimes?

 

[MrMarty51]

After a restart, does it continue to stall ?

 

[Big T]

After a restart, does it continue to stall ?

We do not have a fuel pressure gauge. Per the description from my son, it starts up after two 5 second cranks. That said, it stalled twice on a 10 mile drive. He has video of the event which he is sending to me.

 

[smokymtn65]

Please check extension harness I had a bad one that drove me nuts...

 

[Will L.]

Clear line on ip return- look for bubbles.

After that, do the test of starting truck then opening water in fuel drain valve to see pressure and flow. Catch fuel sample and see how long to get a pint. Let the pint sample settle 15 minutes or more and inspect for contamination. DONT do this test without having a wrench to bleed injectors with you. If the pressure isn’t good you will have to bleed injectors.

A fuel pressure gauge is not a cost. It is an investment. When the lifespan of a $1200 ip is cut in half, that gauge looks might cheap. A person is seriously better to skip an oil change if they have to to To get the gauge in there.

 

[jrsavoie]

I have also had ignition switches give me fits. But never on a 94 or older.

Also had tank sock plug. then when the vehicle was shut off the crap fell away from the sock for a while.

Jumper the lift pump, run about 1/2 gallon out the T drain, Look for crud and water bubbles.

Check grounds. Check wiring harnesses

 

[Big T]

I have also had ignition switches give me fits. But never on a 94 or older.

Also had tank sock plug. then when the vehicle was shut off the crap fell away from the sock for a while.

Jumper the lift pump, run about 1/2 gallon out the T drain, Look for crud and water bubbles.

Check grounds. Check wiring harnesses

Already changed out the ignition switch in the course of troubleshooting this.

Have siphoned fuel out of FFM inspecting for water and none. But will try to do a larger draw and inspection.

It's my son's truck, so I am not driving it. I have a fuel pressure gauge from Harbor Freight, but don't know where to install it.

 

[Jaryd]

Go to the hardware store and get the fittings that you need to plumb it in in between the ffm and ip. Just put a tee in the line.

I bought Leroy’s fuel pressure bolt that replaced the filter drain screw on top of the FFM. When I get time to replace my LEAKING (when I go to the gas station I check the diesel and fill up with oil) valve cover gaskets I’m going to tee my gauge inline between the ip and ffm.

 

[Will L.]

Draw fuel from ffm thru drain valve while running is important part of the test. If nothing comes out and it sucks air in- need to know that.

The 5/16 fuel line (3/8 if FTB mod is done) that goes from ffm to ip: cut that line and install a “T”. Off the T you run the hose to the gauge or the pressure sensor if electric gauge is used.

Some people like to run a metal line into the cab- if so use stainless not copper. I just used rubber. Another thing some people like to do is add an isolator that keeps all fuel from entering the cabin because they don’t use diesel fuel as cologne incase of a leak. Personally i think it’s a dignified scent.

I took mine out and gave it to a good friend moving to Alaska, so have to redo mine during this rebuild. After someone here mentioned gauging before and after filter to see new filter time, I am really considering electric: 2 senders, a 2 pole momentary switch and 1 gauge. Flip switch- pre filter reading for comparison then switch defaults to ip inlet reading.

 

[Jaryd]

@Will L. What’s the deal with not using copper for diesel.

@Big T if you need a quick solution you can go to advance auto or somewhere like that and get a boost gauge and use it for fuel pressure gauge. That’s what I did. Now I can tell if the system ever runs in a vacuum. It’s temporary until I can get time to work on the truck again and install a real fuel pressure gauge with vacuum.

 

[jrsavoie]

hAVE YOU TRIED A KNOWN TO BE GOOD pmd and harness? Might be worth plugging into the IP harness direct with a known good PMD. If that works you are down to the harness or the PMD.

New does not always mean good. What kind of PMD is it?/Where did it come from?

Is the resistor installed?

 

[JMJNet]

It is a 94, if the LP/OPS circuit is not mod-ed with the extra relay, test the LP and there is a chance that the OPS is bad which makes the LP not running as soon as the engine suppose to run.

If it has the extra relay then it should easily be tested for bad LP.

 

[Will L.]

Metals other than steel or stainless steel react with certian bio fuels, ethonal, methonal, etc. Way bigger explanation available on the bio fuel sites.

Mild steel has rust potential and it happens quicker as a fuel line than as say a brake line

 

[ak diesel driver]

If it is a bad OPS than that also means the IP is getting worn.

 

[Big T]

I have also had ignition switches give me fits. But never on a 94 or older.

Also had tank sock plug. then when the vehicle was shut off the crap fell away from the sock for a while.

Jumper the lift pump, run about 1/2 gallon out the T drain, Look for crud and water bubbles.

Check grounds. Check wiring harnesses

hAVE YOU TRIED A KNOWN TO BE GOOD pmd and harness? Might be worth plugging into the IP harness direct with a known good PMD. If that works you are down to the harness or the PMD.

New does not always mean good. What kind of PMD is it?/Where did it come from?

Is the resistor installed?

Stanadyne PMD and extended harness from Leroy. Same symptoms as with the PMD we took off and that was the old black Stanadye PMD, remote mounted.

 

[Big T]

Draw fuel from ffm thru drain valve while running is important part of the test. If nothing comes out and it sucks air in- need to know that.

The 5/16 fuel line (3/8 if FTB mod is done) that goes from ffm to ip: cut that line and install a “T”. Off the T you run the hose to the gauge or the pressure sensor if electric gauge is used.

Some people like to run a metal line into the cab- if so use stainless not copper. I just used rubber. Another thing some people like to do is add an isolator that keeps all fuel from entering the cabin because they don’t use diesel fuel as cologne incase of a leak. Personally i think it’s a dignified scent.

I took mine out and gave it to a good friend moving to Alaska, so have to redo mine during this rebuild. After someone here mentioned gauging before and after filter to see new filter time, I am really considering electric: 2 senders, a 2 pole momentary switch and 1 gauge. Flip switch- pre filter reading for comparison then switch defaults to ip inlet reading.

FTB mod was done, so it has the stainless flex hose and AN fitting to the IP.

 

[Big T]

It is a 94, if the LP/OPS circuit is not mod-ed with the extra relay, test the LP and there is a chance that the OPS is bad which makes the LP not running as soon as the engine suppose to run.

If it has the extra relay then it should easily be tested for bad LP.

I am not certain if the OPS circuit was modified. Is the OPS that harness in the valley with the block resistor on it?

We have the original Walbro FRC 10 from Leroy, fittings, pre-filter, Leroy harness, waiting to be installed.

 

[Big T]

I sold the 2007 SLK 280 today. A buyer from Minneapolis flew out to pick up and drive back. So one less horse in the stable to take care of and I'll have more time to work on the Suburbans. Unfortunately, the proceeds from the SLK only covered a portion of my income tax bill.

 

[Big T]

OK I finally had the chance to drive the '94 around the block today. It sometimes has a slight stutter or miss under heavier acceleration.

I have a fuel pressure gauge, but it's a temporary Harbor Freight model. Intalling a "T" in the fuel line between FFM and IP sounds like a permanent install. I would like to do testing on this in the AM on the 4th. Otherwise, I've been busy with a bathroom remodel project for my sister.