Injection Pump Issue

The place to discuss problems and routine maintenance questions and tips. This is for topics that are specifically diesel-related.
JFink
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Isuzu vehicle(s): 1986 Isuzu Pup 5spd 4x4 w/ 83 2.2L diesel

Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 10:44 am

Hi all. I believe I have an injection pump related issue and I'm a little unsure where to go from here. So to give you a clear picture of what I'm dealing with I'll start from the top.

The truck was running fantastic and I decided to change the fuel filter since it had not been done since I got the truck. Everything seemed to go as planned and I got everything primed as I thought I should. started the truck and went about my day. As I left my driveway I couldn't seem to make any power and the truck was bogging down like I wasn't getting any fuel. I limped it home and scratched my head for awhile. The truck runs and idles as usual but when I rev it up it dies down and then idles really rough. Seems to be getting starved of fuel. Here are the tests I've done so far:

1) Replaced fuel lines with clear lines to see if I'm getting air from the fuel filter to the IP. Everything to the IP looks great, but I'm not getting any fuel from the return side of the IP to the fuel tank. When I use the hand pump on the fuel filter assembly it pushes fuel out the fuel return line though. Also I have the fuel tank cap off to insure I'm not creating a vacuum issue

2) Removed and cleaned the banjo bolts on both and input fuel side and return side. Didn't see any build up in either when pulled. Cleaned thoroughly and put back in place. No change in running condition.

3) Just to be sure I didn't have a vacuum issue I ran the fuel supply line feeding the fuel filter into a jar of diesel and this didn't make any difference. I also bypassed the fuel filter assembly completely and used a vacuum pump on the return side to pull diesel through the IP. None of this made a difference in how the truck ran. Still idles and eventually I don't see any fuel coming out of the return line.

So now I've done some research and realized that there is a fuel cutoff solenoid on the IP that I did not know of. What controls when the fuel is cutoff with this solenoid exactly? Is it just lack of power from the ignition being turned off or is there additional logic controlling this solenoid? I'm still without a shop manual at this point since I just got the truck so I'm researching everything I can online. Also, I'm curious about the lift pump failing on the IP. Anybody have a detailed drawing of the IP they'd be able to share? Thanks for any advice you all might have.

dorf
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Re: Injection Pump Issue

Postby dorf » Mon Jul 27, 2020 12:59 pm

Since problem started after filter change....I'd assume your problem is in that area

Bottom seal on filter where the drain valve .water float is located would be suspect and or the valves in the filter assembly.

Sounds like you are sucking air via a pinched seal.

If you can install pressure gage...pump up system. See if holds pressure over night ..might be able to isolate.

Just my 2 cents

JFink
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Joined: Sun Jul 26, 2020 12:10 am
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Isuzu vehicle(s): 1986 Isuzu Pup 5spd 4x4 w/ 83 2.2L diesel

Re: Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 1:28 pm

Thanks for the input. I've bypassed the filter completely with a jar of diesel feeding the IP and pulling fuel through the IP with a vacuum pump at the return side to prime the system and I'm still having the same issue with the engine running rough. I believe this would rule out the filter or plunger being the issue. I've also installed clear fuel lines to watch for air in the lines and do not see any air traveling through the lines feeding the IP. Only the return line goes empty once the truck has been running for a few minutes.

dorf
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Re: Injection Pump Issue

Postby dorf » Mon Jul 27, 2020 2:37 pm

Have you ,,,,cracked. Open the injector lines ....one by one when Running....

To see if one makes a difference

I'd pump it up with a pressure Gage installed in original. Configuration.....and isolate.

I Still say you are sucking air someplace

dorf
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Re: Injection Pump Issue

Postby dorf » Mon Jul 27, 2020 2:58 pm

I guess I need add...you will need source of positive pressure to pump,up the system...such as a marine pump up squeeze bulb...like for outboard motors.

Attached to the input side of the filter housing..

Should hold pressure over night.....about a 1 pound or so.

JFink
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Re: Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 3:56 pm

Ok so I've proved that I am not getting any air in from the filtration system before the IP. This includes all hoses as well. So that would make the likely culprit of an air leak on the injection pump itself. I'm not very well versed in the construction of these IPs and the areas most likely to fail on them. So what would be your go to areas to check for leaks on these guys?

I have also cracked the lines leading to the injectors like you said and had diesel purging out of each injector fitting. Also, while the truck is running rough I can press the filter plunger and the engine will start running normally and fuel will then come out the return line as normal. So this does make me believe there might be air getting in somewhere on the IP. Just unsure where a likely spot would be

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Paul
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Re: Injection Pump Issue

Postby Paul » Mon Jul 27, 2020 4:04 pm

Seems like you have covered most of the troubleshooting bases pretty well. The pump may have a problem but they seldom go bad as quickly as yours has. The fuel shutoff solenoid is controlled via the ignition switch and is powered by the second fuse from the firewall. No Computers here. Also, the solenoid is either on or off, as far as my experience and should not cause an idling only fault.

I cannot think of any other cause for your symptoms unless one of your tests is missing something. Seems you do have the pump body full of fuel, so should be pumping. All in all, seems like fuel starvation for sure, can't see why.

The fuel control sleeve could be stuck in the idle position, but again seems unlikely. Any chance you are running on WVO which can gum things up?

Here is an illustration of the pump:

Pump bLow up with torque specs.jpg


This one does not include the CSD. Click on image for an enlarged view.

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

JFink
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Isuzu vehicle(s): 1986 Isuzu Pup 5spd 4x4 w/ 83 2.2L diesel

Re: Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 4:34 pm

Thank you for the image. That will help with the troubleshooting tonight. As for WVO, no. It's only seen pump diesel since I've had it. I was also thinking about trying the transmission fluid trick and pumping it through the system and letting it sit overnight and seeing if the detergents break any potential blockages down. I'll give that a shot after a thorough air leak check on the IP.

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puttputtinpup
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Re: Injection Pump Issue

Postby puttputtinpup » Mon Jul 27, 2020 5:49 pm

Problems began with filter change let's focus there. What brand filter and number did you install? Micron rating? Perhaps change the filter again using a different type. I used to get my Purolator fuel filters from advance auto. Yours seems to be running lime mine did when the filter was clogged.

dorf
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Re: Injection Pump Issue

Postby dorf » Mon Jul 27, 2020 6:09 pm

Good point on the filter

At one time I used a Duramax assembly......micron rating was too fine.....reduced performance

When I used a OEM FILTER..problem disappeared.

Lastly.....use a positive press Set up and spray soapy mixture.....all over look for bubbles

Be sure to notify us as to the FIX...

JFink
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Isuzu vehicle(s): 1986 Isuzu Pup 5spd 4x4 w/ 83 2.2L diesel

Re: Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 6:17 pm

I'm just not sold on the filter assembly being the issue anymore because I've completely bypassed it out of the equation a few times now with a jar of diesel ran straight to the IP and still had the same results with no flow out of the return line. I think that should rule the filter assembly out completely.

I'll try a pressure test with soapy water and see what I can find. Updates to come. Thanks fellas.

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puttputtinpup
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Re: Injection Pump Issue

Postby puttputtinpup » Mon Jul 27, 2020 6:35 pm

Crank engine over with lined to injectors cracked open til a bit trickles out of each. When you bled the pump, did you have the fuel solenoid energized w switch on?

JFink
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Re: Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 6:45 pm

Yes, I had the ignition energized so the solenoid should have been open while bleeding through the pump.

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Paul
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Re: Injection Pump Issue

Postby Paul » Mon Jul 27, 2020 9:52 pm

JFink wrote:Yes, I had the ignition energized so the solenoid should have been open while bleeding through the pump.


Fuel can be bled through the pump housing without the solenoid being activated. The solenoid controls the fuel inlet to the high pressure pumping chamber & hence to the high pressure lines to the injectors.

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

JFink
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Posts: 13
Joined: Sun Jul 26, 2020 12:10 am
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Isuzu vehicle(s): 1986 Isuzu Pup 5spd 4x4 w/ 83 2.2L diesel

Re: Injection Pump Issue

Postby JFink » Mon Jul 27, 2020 9:55 pm

I did notice this while using the plunger once without the ignition turned on. Wasn't exactly sure why it worked but that answers that thought. Thanks for the update