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´94 Chevy Suburban stalling, problems idling and dificulty to start engine.

Question: 
1K views 17 replies 5 participants last post by  san15895 
#1 · (Edited by Moderator)
Hi, as I said in the title, I´m having some problems with my 94 suburban.

First thing I´m concerned about is that today I could finally start my engine changing my PMD. I have it relocated but still the one that was in the truck stopped working. What could cause a relocated PMD to fail?

Second, sometimes the truck runs great, but suddenly it stalls and after i can start it, it idles badly. Feels like RPM's are fluctuating and it loses power. It feels amplified when I put transmission on D or R.
Here is a video showing how it sounds (there is other truck on because my batteries were down and I used some cables). It´s not very clear in the video, but i hope you get it.



I´m getting codes 17, 18, 29, 35 and 36 by the SES light blinking.

Help me please!
 
#2 · (Edited)
Welcome to DieselPlace
Start by changing the fuel and air filters. Also, make sure the small filter screen down inside of the bottom of the fuel filter manager is clean as well.

Go through all of your grounds: https://www.dieselplace.com/forum/showthread.php?t=163087

Remove each ground, clean the contact points and re-install. Replace any ground wires that are in bad condition.

Perform a lift pump test: https://dieselplace.com/forum/showthread.php?t=39350
If the lift pump fails the test, be sure to replace the OPS ( Oil Pressure Sensor) as well.

Install a clear piece of fuel line on the return side of the Injection Pump to help locate any air in fuel gremlins:
https://www.dieselplace.com/forum/6...-5l-td-pmd-resistor-settings.html#post7305306
 
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#3 ·
Thanks for your reply. I´m form Argentina, and i don´t have easy access to any parts. Recently I ordered the speed sensor and the VSSB and it took almost 2 months to get here.

This is why I want to diagnose the exact problem first.

Now, I have cleaned my fuel tank and all the circuit a month ago. Still, I have the clear fuel line in the return of the IP with a big buble of air.

I will check all grounds asap and the lift pump as well.
 
#6 ·
Do you have an acdelco fuel filter? (That's really the only filter you should use because the air bleeder valve works properly on those)

Anyway...

Good way to test lift pump and bleed air at the same time...

Use a clear plastic hose... attach to nipple on air bleed valve on fuel filter located at rear of engine towards firewall. Put the other end in a jerry can. Twist the bleeder open and purge the air out of the fuel system. Open the valve only with the motor running... you'll see the air bubbles leave... and if the motor stalls while your attempting this... the l.p. is bad. Replace with acdelco l.p. only.
 
#9 ·
As I said, here in argentina it´s difficult to get access to those parts. I could order an acdelco fuel filter, air filter, etc. But I want to make sure that i don´t have to order anything else haha.

I will try to solve the air problem first, then I will be able to go for other problems.

Thank you! I will test the LP and let you know.
 
#13 ·
So, I started the engine and drove the truck a few miles. Still running badly.
I stopped and start doing an inspection of the fuel lines touching hoses and some conectors.
After not seeing any damaged hoses or cables I started the engine. It runs great..
I kept touching the same conectors again, with the engine running. When I disconected the optical sensor above the IP, the truck stopped just as if I took the ingnition off.

Then I started the engine without the sensor and It still runs..

I really dont know what the conclussion would be .. could the problem just be rusty connectors?

As for the air bubbles I noticed that when the engine IS running no Air bubbles appear to be in the return line
 
#14 · (Edited)
If you touched electrical connectors and the engine ran better then I would look at all of the engine electrical harness ( looking for rubbed through wires, broken or frayed wires, loose connectors) etc...


I would still pressurize the fuel system and look for any fueling issues to be on the safe side.
 
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#16 ·
It's also pretty common to have air intrusion (fuel leaks) form in the ffm (fuel filter manager) e.g. the fuel filter housing...

The water in fuel sensor o ring likes to go bad(the do-dad on the side), along with he fuel heater o ring seal (on the bottom)... the fuel heaters location combined with the overall location of the ffm can make this a difficult leak to spot.

Figured I'd point out the ffm as a possible cause for air intrusion. If you can't find ANY leaks... anywhere else... that's a good place to find them...
 
#17 ·
It’s pretty common to have 1 small air bubble in the clear return line when the engine is NOT running. Mine has a bubble every time I shut it off but goes away as soon as it’s running again.

Air in the return line while running is a problem
 
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