M923-A2 wont start. done everything

[buggin]

Hello
I have a M923-A2 that wont start. Its a 2011 rebuild. It would not start on base, so I had it towed home. It will start on ether. I removed the fuel shut off solenoid. Kill switch off on dash and manually checked under hood, its in the correct position to allow fuel to pass. I pressurized the tank with air. There is fuel past the primer pump. Still nothing.
The only thing that I notice it does differently when priming is that on working a2s you can hear it spraying into the injector, on this one I cant get it to that point. What can I do next to try and get it started. Im guessing its a bad injector pump? Unsure. Does anyone have any ideas what it could be? Or what else I can try? Thanks for your time.

 

[Reno]

Here is what happened to me.
Mine always easily started then one day nothing.
Turned out to be cracks in old fuel lines allowed it to suck enough air into the system, it wouldn't prime.
Fuel lines are cheap, great store in town actually gave them to me for free, took only minutes to replaces, solved problem.

If it cranks fine and you see no smoke out exhaust it means it is not getting fuel to injectors.

I thought it might be my injector pump because I could see I would get fuel to injector pump when cranking but, nothing went to injectors. It would fire easily on ether. Turns out I wasn't getting enough fuel to build proper pressure to for injector pump to work. I should have done a fuel volume test but didn't.

Here is what I noticed with mine. I would keep trying to prime it with the manual pump on the block and noticed lots of air while trying to bleed it at the 10mm nut by the fuel filter on the engine block.

I filled a gallon jug of diesel then put the fuel line just below the primer pump into it. Primed it. Then it fired and ran fine.
That told me the problem was somewhere between the prime pump and the tank.

I pressured the tank and finally was able to see some fuel leaking from the fuel line that runs from the large fuel filter back to the frame rail fitting.

From my understanding, if the fuel line can allow air in, after it sits for a while, the fuel will return to the lowest point (i.e. tank) and air will replace it in the lines. Then when you try to start it, it won't until all that air is replaced again with fuel.

Before you pull out the injector pump, first always check the fuel shut off solenoid at the pump, of course make sure you have enough diesel fuel in the tank. Check fuel volume to pump.

Also, there is a check valve on the injector pump. This is suppose to open once the injector pump receives the correct fuel pressure. If it is stuck open, the injector pump won't build enough fuel pressure to send to the injectors. It is simply the fitting that allows the extra fuel to return to the tank. You can test it by pinching off the return line attached to it.

I have also heard of bad fuel or algae in the fuel not allowing it to start. As a note, mine symptoms also began when I was down to a 1/3 of a tank.

Hope this helps someone out there and saves you some headache and money.

 

[Evil Dr. Porkchop]

I'd check the fuel lines. I worked on one that would prime fine, and run ok sometimes (for hours with no problems), other times it would die during warm up. The fuel line leading to the primer was cracking and was the cause of the problems.

 

[R Racing]

bad fuel lines!

 

[Carlo]

Same story. Different truck. Fuel lines sucking air. It's so common it hurts!

 

[Scar59]

Same story. Different truck. Fuel lines sucking air. It's so common it hurts!

My buddies A2 had the same exact issues, fuel lines, fuel lines, and fuel lines. Start replacing from the tank and work forward.

 

[Carlo]

My first post on SS was asking fir help on the same problem. Juan and stein and allot if other 5 star brothers helped me.

 

[buggin]

I'll work the fuel lines. Thanks. I'll keep you posted.

 

[74M35A2]

When you are pressing the prime button, the spray you normally hear is the pressure relief bypass valve opening on the injection pump, it is not spraying into an injector. Just FYI to help your understanding, which helps troubleshooting. When you are pressurizing the tank with air, the cracks in the fuel tank lines won't show up, as all others here are saying. You could confirm by running a separate suction tube to the mechanical pump, and the engine prime, you'll get your "squish" sound during priming, and will take off and run perfectly. Also check the bolt on top of the large canister fuel filter. It has a square washer, which if not seated correctly, may or may not allow the system to suck air. Schrader valve at the top of that canister head too that should be working correctly, they seldom fail.

The only way to really prime correctly is to crack open the bleed port on the injection pump, believe it to be a 10mm, located at the pump front, on the engine side of the pump.

 

[wreckerman893]

The only way to really prime correctly is to crack open the bleed port on the injection pump, believe it to be a 10mm, located at the pump front, on the engine side of the pump.

My resident wrecker will not start if it has been setting more than a few hours after being shut off. I have to bleed through the above mentioned screw to get it to start. Once I figured that out (with a lot of help from the peanut gallery here) I can crank it every time. Still can't figure out why it does this.

 

[Alexsha]

I need to replace some/all of my fuel lines as well. Why isn't there a fuel line kit for these trucks? That would be convenient.

 

[ke5eua]

I need to replace some/all of my fuel lines as well. Why isn't there a fuel line kit for these trucks? That would be convenient.

Easy way is to take the old ones off and go to a hose shop and get new ones made.

Don't be like me and spend 65+shipping on the hose that goes from the filter to the ip on the a0.

 

[98G]

I need to replace some/all of my fuel lines as well. Why isn't there a fuel line kit for these trucks? That would be convenient.

I'll bet you could put a kit together and sell it at a profit. People are generally willing to pay for convenience.

 

[ke5eua]

I'll bet you could put a kit together and sell it at a profit. People are generally willing to pay for convenience.

So true, as it was in my case. Ended up having to go to a semi shop anyway so the connivence was quickly defeated.

 

[buggin]

I put new rings in the primer pump. I've pressurized the tank several times and I can't find any leaks in the fuel line. The lines look brand new, propably replaced in 2011 with the rebuild. I also pinched off the return line to see if the valve was stuck open in the fuel injector. Still no start

 

[Carlo]

You would be hard pressed to find fuel leaking from the hoses. They suck air so there is no fuel seepage. Try getting a short hose and get the fuel direct to the pump from a small can of fuel eliminating the fuel tank, filters and hoses. Prime it sons see if she fires. If she fires it's your hoses to the tank. If she does not fire you have eliminated allot of possibilities.

 

[Scar59]

The fuel feed line in the tank may have a split above the fuel level. Replace that pick up line, it's cheaper than filling the tank.

 

[Warthog]

From post #2 he said to use a jug of fuel with an extra hose. Thus bypassing the fuel lines.

Here is something that I used to prime the system in a M35A3 CAT fuel system.

I bought a bug sprayer and some fittings. I bypassed the fuel tanks and all the hoses and fittings. I plumbed the bug sprayer directly to the injector pump. Pressurized the system and the engine fired right off.

Don't know if it will work with the 8.3L but it is worth a shot.

 

[Alexsha]

This might be a silly question, but regarding the fuel lines attached to the top of the tank on a M923A2, what material are they made of?

 

[davo727]

Copper