Will not start after installing injector pump

Tiny
PAPRMKR
  • MEMBER
  • 2001 ISUZU TRUCK
  • 4.8L
  • 4 CYL
  • TURBO
  • 2WD
  • AUTOMATIC
  • 325,000 MILES
Engine is a NPR diesel. After removing and installing injector pump to access oil cooler my truck will not start. I removed and installed pump following timing mark instructions. Marks are spot on. I was unable to prime using the hand pump so I filled the fuel filter up and let it bleed the line to the pump by gravity. I verified the fuel cutoff solenoid is working correctly by removing the back pump cover and applying 12 volts DC. I have no fuel at the injectors and no voltage at the glow plugs. When removing the line from fuel filter to pump I can see there is fuel in the pump. The injector pump has a one wire connector to the solenoid on top and a 4-6 wire connector going to the bottom of the pump. The pump model # is Zexel107492-1080T. Any suggestions appreciated and also where is the EFI relay located please?
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Sunday, September 27th, 2020 AT 6:46 PM

7 Replies

Tiny
MOTOR MASTER
  • EXPERT
Hello my name is Dave

I would like to begin by making sure you have replaced the fuel filter before coming to any conclusions about a faulty pump, if you haven't we need to start there. I would also recommend that if you have access to an air compressor take a blow gun and disconnect the fuel line at the fuel filter that runs back to the tank, take the fuel cap off and blow back through the fuel line that runs from the filter to the tank. You don't have to worry about an in tank filter it has none.

I am very familiar with these trucks and next thing I want to check is that the pump is getting fuel, a major problem I ran into with theses trucks is rust in the fuel tank contaminating the entire system, this is why I recommend blowing the line clear. Regardless I would recommend going to Harbor Freight or a similar store and buy a magnetic tool holder and go to the hardware store or similar and buy a very strong tape, I used metallic duct tape, and tape it to the bottom of the tank to trap the rust at the bottom to keep it out of the system. Rust is by far the most common cause of any fuel issue with theses truck and the most likely suspect for a fuel pump failure.

The reason this happens is the new(er) low sulfur fuel is more susceptible to water contamination because the sulfur would bond to the water dispersing it throughout the fuel were as the new fuel allows the water to accumulate at the bottom of the tank causing it to rust.

Your pump is purely mechanical so as long as the cable from the shut off solenoid moves it should start, the wire on the top is for the pump advance and the other wires are for the crank sensor however none of which can keep the truck from running.

I would start by taking the feed line off the injector pump that goes from the lift pump on the side of the injection pump and make sure you are getting fuel into the injector pump. If you are getting fuel to the injection pump and get no fuel when you loosen the fuel line(s) on the top of the pump and the shut off is moving then you have a faulty injection pump.

If you are not getting fuel to the injector pump I would get a container of fuel and disconnect the suction (input) hose from the lift pump, put a longer hose on it and place it into the container of fuel and see is this allows the engine to start. If it doesn't I would recheck for fuel to the injector pump and if you don't have any then you have a faulty lift pump, and it will pump regardless of the shutoff's position.

If you can get fuel by connecting a temporary line to the lift pump, and you have replaced the fuel filter and cleared the fuel line going from the filter to the tank there is the possibility the filter housing is restricted, you can determine this by bypassing the filter temporarily connecting a hose from input hose fitting to the output fitting. These steps should track down your fuel issue, and it would be unusual for it to be a mechanical issue with one of these engines, When I was service manager and lead mechanic for a good size fleet of these trucks actual engine failure takes a HUGE amount of abuse, we had several trucks with over 600,000 miles that didn't even use an excess amount of oil between service intervals.

I believe this will help you track down your issue and if it doesn't let us know and we will do our best to help you further. Please keep us up to date on your progress and thank you for using 2CarPros!
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Monday, September 28th, 2020 AT 4:03 AM
Tiny
KEN L
  • ADMIN
Here is a guide to help test the EFI main relay and the location in the diagrams below:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Monday, September 28th, 2020 AT 12:06 PM
Tiny
PAPRMKR
  • MEMBER
Thank you Dave,

I'm going to try bypassing the fuel filter. Can you tell me do I have an in tank fuel pump? This is the 4HE1 diesel engine.
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Tuesday, October 13th, 2020 AT 5:22 AM
Tiny
PAPRMKR
  • MEMBER
Bypassing the filter made no difference. There is no in tank pump, just the lift pump on the side of the injector pump. I found this link I guess I will try: http://ww2.justanswer.com/uploads/jettadan1/2010-11-10_212034_1393994.pdf
I don't see a throttle position sensor anywhere on this engine though.
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Wednesday, October 14th, 2020 AT 6:30 PM
Tiny
4DRTOM
  • EXPERT
Hello,

I have found sometimes is take a fair amount of cranking to get the fuel all the way to the pump. Enough that you need to stop before the starter gets over worked. I feel the positive cable and stop once it starts to feel warm let it cool then try again. By this time the fuel should be at the motor. I crack the fuel line coming from the tank at the injector pump crank until it leaks at the spot, then tighten back up. Then crack the line that goes to the farthest injector at the pump and crank until it leaks a bit. Once the fuel is that far your close crack that same line at the injector crank until it leaks at the injector. At this point tighten it and you should start to get some ignition and emission out the tail pipe. Keep the gas pedal floored and crank until it fires up.
Tom
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Thursday, October 15th, 2020 AT 9:46 PM
Tiny
PAPRMKR
  • MEMBER
I have cranked it very much with no result. I have fuel all the way through the pump even coming out of the return line to tank. Just none coming from the pump to injectors. I was wondering if a relearn for TPS is the issue as described in the previous link I posted. After reading this article it makes me wonder. https://www.atsg.us/atsg/blog/oldervehiclesarenotnecessarilyeasiertofix/
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Friday, October 16th, 2020 AT 4:06 PM
Tiny
MOTOR MASTER
  • EXPERT
Hello again, no there are no in tank pumps on those engines, the lift pump attaches to the side of the injector pump. There is nothing electronic for that engine however there is a TPS on the accelerator pedal but it is there only for regulating the transmission and there is no relearn process for it. When operating properly that engine will run with no electricity at all, it is strictly a mechanical engine with the exception of the electronic advance which only has a minor effect on the engine, in fact you would most likely not notice if it wasn't working.

When you bypassed the fuel filter did you still have it feeding from the tank or did you put the line into a fuel can? I would make sure to try putting the line that goes from the filter to the engine in a container with fresh fuel. Like I said before a clogged line from the tank to the filter is one of the most common problems with these trucks and this will eliminate that as a cause to your problem.

Since you have fuel coming out of the return hose I would crank it for a while then immediately pull the injectors and see if they are wet with fuel. The other thing we should look at is the condition of the fuel, if there is a lot of water in the fuel it's not going to start. You can open the drain on the bottom of the fuel filter and see how much water comes out and also fill a glass jar with some fuel and let it sit for about 15 minutes, if there is an excessive amount of water you will see it settle to the bottom of the jar. If that is your issue there are additives to remove it however if it is extreme I would recommend pumping the fuel out and refilling it with fresh fuel and replacing the fuel filter.

If you can perform these steps and let us know the results we would appreciate it and thank you for using 2CarPros!
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Monday, October 19th, 2020 AT 4:30 AM

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