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1993 i shut it off,now wont start unless i bleed injectors

9K views 27 replies 7 participants last post by  MrPurple 
#1 · (Edited)
Help.
I have a 1993 12 v, all stock other than 90 hrs injectors and pump turned up. I put this engine complete with the getrag in my 1979 crew cab. Very minimal electrical etc. The truck has been stone reliable until recently. The starter went south,the truck sat about a month until I could get around to replacing it. Anyways after the swap, truck started as always. Drove over to a friends house and shut it off. Well guess what, no start. FSS is ok, I could get it running while bleeding the injectors, and unit runs very well when running. As soon as I shut it off, no start until I bleed injectors. Thought I had a bad injector, sent them all out for a rebuild, they are all good. Absolutely no issues. Installed them, bled system,truck runs strong but will not start unless I bleed a few injectors. Weird..Possible plugged return line? Im out of ideas. Injection pump and injectors were both rebuilt a few years ago. ood fuel between lift pump and inj pump. when im bleeding the injectors there is air in the system. It dosnt matter if I try to restart 5 sec or 10 min after shut down.
 
#2 ·
Sounds like you're sucking air from a bad fuel line somewhere. When it's running it probably just passes through the injectors but when you shut it off it all collects into an air pocket. A lot of guys on here say to stuff a rag in you filler neck with and air nozzle and pressurize the tank. This should push fuel out and holes that normally wouldn't leak fuel out but let air in. Don't go to high with the pressure though you can damage the injection and lift pumps. You should only need 10 psi or so.
 
#3 ·
Instead of bleeding the injectors try bleeding the LP. If you are getting air bubbles there every time check for a bad fuel line or pickup in the tank.
 
#6 ·
Ok. I dropped the fuel tank finally. Upgraded stock 3/8 pick up to 7/16 Removed all fuel lines and replaced with a one piece steel 7/16 line with a electric pump at the fuel tank regulated to 6psi.at h20 separator. Bypassing stock lift pump all together. The truck runs good as new now. Thanks for all the help guys. The issue was a hole in my stock fuel line. As was suggested.
 
#7 ·
If it doesn't start on first crank check for air or a FSS wire off.

Glad to hear it is fixed.
 
#8 ·
Not to highjack a thread but my question is so similar I can't help but ask. Every morning when I start my truck it runs rough for about 30 seconds then the idle goes up and it clears out and runs great.

Sounds like it is getting air in the system somewhere. My fuel pin has a very minor leak, when I pull the afc top off there is a thin film of diesel fuel inside, could the leaking o-ring cause this scenario or should I look at the fuel system?

The previous owner installed a holley black pump and it is mounted above the injection pump, could this cause a problem also?

The truck starts on the first crank but idles rough until clearing out 30 to 60 seconds later after it sits for an extended time.
 
#9 ·
Sometimes when first started especially when cold out it can run a little rough, usually just idle up to about 1,000 RPM's and it should clear up faster.

That small amount of fuel in the AFC won't cause any starting or running problems.

How much fuel pressure are you running with that pump? The stock LP puts out 3-5 PSI, you have to be carefull running to much over 12 PSI or you could blow the front seal out the IP.

The more fuel pressure you have the more chances of leaks you could get.

Is your gridheater working?
 
#10 ·
The fuel pressure is between 10-12psi, I have a gage on it. The grid heater works also. There is definitely something not right when it first starts up, I have owned 3 of these trucks and this one has an issue.

Though it is relatively minor since it does clear up and usually wont come back all day if started and stopped continuously, just over night it appears it gets air in the system and idles low and runs rough. What is odd is that it corrects itself almost as if someone flips a switch, goes from running like crap to straightening out all of a sudden.
 
#11 ·
Sounds like maybe you could have a start of air getting into the fuel system.

After it has sat for a few hours open the bleeder and manually pump the LP to see if any air bubbles come out the bleeder. If any bubbles came out it should fire right up and run like normal.
 
#13 ·
If your sucking air into the fuel system it will be in the injection pump and injector lines also.
 
#15 ·
If your getting air into the system you'll have to crack injectors lines to get it out so it will start.

You need to find where it's getting it in and repair it, probably old fuel lines.

Before starting it next time after it has sat bleed the filter to se if any air bubbles come out.
 
#17 ·
When you check for bubbles are you letting the truck sit for a hour, so if any bubbles are in the filter they are at the top?

Some will try to start on 4 cyls most will on 5 cyls.
 
#19 ·
How much fuel pressure you have?
 
#21 ·
It needs to have at least 3 PSI for it to start like it should.
 
#22 ·
Leak points.

There's a rubber seal in the 2-piece fuel line between the fuel filter and the injection pump. If it has a pinhole, that would do it. If you have that stupid fuel heater plastic POS between the filter and the head, that could be leaking. If you had a leak on the pressure side (after the pump) it would spray fuel. Your leak is between the IP (or at the suction side of the IP, perhaps) and the fuel tank. Reseal it all.

-pull the line off at the IP, clean, reseal, reinstall.
-pull the 2-part line apart and replace the seals, or replace the whole line.
-pull the inlet fitting off the lift pump; inspect the lift pump carefully to see if the housing is cracked around that pipe fitting; super easy to break the pump in this spot by overtightening.
-replace the lift pump; you could have a diaphragm leak sucking air.
-replace the sealing washers on the fuel lines.
-replace the soft line between the fuel tank and the lift pump. Buy the best line you can; like transmission line. The cheap stuff is pretty crappy these days; I recently had some AutoZone fuel line turn to putty after 6mos in my rig and it saw nothing but diesel.
-replace the fuel filter
-if you have a fuel heater, get rid of it. Get the shorter spud and install the filter right on the head.

In all, you're looking at maybe $100 in parts and will have changed every part on the low pressure side. If that doesn't fix it, your IP has to have a leak somewhere. It's definitely not on the high pressure side or between the injectors and pump or you'd have diesel on the ground.
 
#24 ·
There's a rubber seal in the 2-piece fuel line between the fuel filter and the injection pump. If it has a pinhole, that would do it. If you have that stupid fuel heater plastic POS between the filter and the head, that could be leaking. If you had a leak on the pressure side (after the pump) it would spray fuel. Your leak is between the IP (or at the suction side of the IP, perhaps) and the fuel tank. Reseal it all.

-pull the line off at the IP, clean, reseal, reinstall.
-pull the 2-part line apart and replace the seals, or replace the whole line.
-pull the inlet fitting off the lift pump; inspect the lift pump carefully to see if the housing is cracked around that pipe fitting; super easy to break the pump in this spot by overtightening.
-replace the lift pump; you could have a diaphragm leak sucking air.
-replace the sealing washers on the fuel lines.
-replace the soft line between the fuel tank and the lift pump. Buy the best line you can; like transmission line. The cheap stuff is pretty crappy these days; I recently had some AutoZone fuel line turn to putty after 6mos in my rig and it saw nothing but diesel.
-replace the fuel filter
-if you have a fuel heater, get rid of it. Get the shorter spud and install the filter right on the head.

In all, you're looking at maybe $100 in parts and will have changed every part on the low pressure side. If that doesn't fix it, your IP has to have a leak somewhere. It's definitely not on the high pressure side or between the injectors and pump or you'd have diesel on the ground.
I think that most of your tests or fixes are not requires . There is NO air between bleeder and fuel tank.

I don't know if it is getting air past this point

Is it possible for injectors are an issue
 
#28 ·
I had the same issue with my 1990, I installed an electric fuel pump before the LP, running at 7-9 PSI, I only useful for startup. I know it's a band aid fix, but I haven't had any issues since, and instead of spending a day looking for leaks, I spent an hour putting in a pump. Make sure if you do this that it is between the LP and the tank, not between the LP and the IP. LP with mess with with flow if the cam stops in the wrong position.
 
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