M923a2 no start question

[Swamp Donkey]

Yes, throttle linkage is still off, haven't found the ball & joint yet.
Ill give that a try tomorrow & report back.

Is this the ball joint coming off the bracket back at the floorboard? I'm not sure if the A2s have more than one, or if it's in the same place as on the A0/A1s since I don't have one. I can point you to a replacement but I need to make sure it's the same across all the models.

 

[Jbulach]

Are you sure you have fuel in the tank? Sorry, couldn't resist! Hopefully, WillWagner s last EASY solution is it!!


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[WillWagner]

Are you sure you have fuel in the tank? Sorry, couldn't resist!藍 Hopefully, WillWagner s last EASY solution is it!!


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There is fuel to the pump, but he has not yet verified the pressures. If the WOT won't make it fire, the pressure check is a must.

 

[Jbulach]

So... inlet pressure 15 PSI minimum, 25 PSI ideal?


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[WillWagner]

15 to lite. 25 is good, 30 is better. The lift pump is capable of 70 psi.

 

[74M35A2]

My truck has a brass fitting & copper tubing in the tank.
All of the fuel system is good, this is NOT a loss of prime issue.
This is an issue INSIDE the IP not letting fuel to any of the injector lines.

Thanks for your suggestion though.

Don't ding him so fast. You don't know why it is not spraying fuel. Very rare for these pumps to fail, I think only a single case on SS?. Like others said, it may be sucking a small amount of air and not pressurizing the barrels.

Measure inlet fuel pressure, verify pump drive, then pull back cover and check fuel rack travel. There are several test ports provided to measure the pressure. One is at the lift pump.

 

[WillWagner]

No dings, this is just a stumper. It is sort of common, seen MW and P pumps fail quite a bit. Mostly due to h20, some from governor parts flinging thru the hsg and some just a plain old no start. He just needs to check pressures to verify/confirm pump issue.

 

[snowtrac nome]

i was working on an Isuzu today,with a knock off bosch pump made by zexyl . it had the same problem there is a fuel plunger and barrel under the delivery valve.the plunger or barrel is scored when the plunger comes up it sticks and suddenly no fuel. I could tap it and get it to return but no luck,some thing is scored going to have to send the pump in for a rebuild. I have a sneaking suspicion that is your problem especially if there is a chance water or air has run through it.

 

[86m1028]

Had a little time to jack with it today.
Just to recap
IP IS getting fuel, return line check valve does seem to be functioning properly.
Throttle linkage is NOT attached at this time, I need the ball & socket that attach the throttle linkage to the lever that moves the throttle shaft on the IP.
I DID get it to start by having the throttle shaft off idle. I did turn external idle set screw up 2 full turns, NOW it WILL start & idle.
At this point I have NOT checked fuel pressures at pump, need to get gauges.
My thoughts now are it's an issue with the governor.
As long as the throttle is not at rest it will start, it will rev up a few times per me moving the throttle lever but 3rd to 4th
rev it revs real slow & if I release the lever to idle it will die.
Feels like governor is fighting its self or something inside IP. Engine speed raises & lowers then either levels out or dies.
When running it does seem to idle rougher than before, causing stuff on truck to vibrate.

Can someone point me to detailed info on the IP itself ?
Exploded view, parts names, pressure testing ports & diagnosing.

Thanks for all your suggestions & posible issues.

 

[WillWagner]

It could just be idling really low, that could be why it was a no start and why it shakes now, idle should be 650-750 RPM. There is a lever behind that the plate your throttle linkage bolts to. There is an acorn headed bolt that contacts a tab on that lever, this is low idle adjustment. It is very common for that bolt to wear bed enough to let the idle drop so low the engine will not start until the pedal is depressed and will not stay idling. It is also a big possibility that soldier B used the joints on the truck throttle linkage to adjust idle speed and the pump idle speed was never set....possibly the cause for the failed ball joint on your linkage, never being truly at rest, always having the pressure of the pump throttle linkage pushing on it?

Check pressures at the circled port, that is supply to the pump from the low pressure pump. Follow that line back to the filter head. Look for the line coming from the lift pump to the filter head. Check pressuer there. The difference between the two is your pressure drop across the filter....IIRC, 4 psi is max, I might have to look it up. The pressure at the port on the pump is the fuel pump galley pressure. An OK pressure is 15 at idle and when the engine is at WOT, 25 is OK. A good overflow valve will show 20+ at idle and greater than 30 at WOT. If the pressure isn't there, 1 of two things, an overflow valve or a lift pump. The pump banjo fitting is 14mm and the filter head fitting is 12mm.

Edit...the white circled area is the low idle adjustment

 

[WillWagner]

And for the helluv it, the FSOV measurements,

 

[Swamp Donkey]

Throttle linkage is NOT attached at this time, I need the ball & socket that attach the throttle linkage to the lever that moves the throttle shaft on the IP.

Is it #23 or #18 in the diagram below?

 

[86m1028]

Is it #23 or #18 in the diagram below?

View attachment 667185

Yes, that's it.

Thanks

 

[Swamp Donkey]

Which one, #23 or #18? They are different.

 

[86m1028]

Which one, #23 or #18? They are different.

It's #23

 

[Swamp Donkey]

PM sent.

 

[86m1028]

PM sent.

Thanks Mark.

 

[74M35A2]

i was working on an Isuzu today,with a knock off bosch pump made by zexyl . it had the same problem there is a fuel plunger and barrel under the delivery valve.the plunger or barrel is scored when the plunger comes up it sticks and suddenly no fuel. I could tap it and get it to return but no luck,some thing is scored going to have to send the pump in for a rebuild. I have a sneaking suspicion that is your problem especially if there is a chance water or air has run through it.

Zexel is Bosch's Japan division. Not a knock off. Commonly found on Kubota, etc.....

I'm still guessing he has a slight air ingestion, and would also not build delivery pressure due to it. Did he mention if the suction side hoses were replaced? Nearly all are leaking by now if not.

 

[86m1028]

Zexel is Bosch's Japan division. Not a knock off. Commonly found on Kubota, etc.....
I'm still guessing he has a slight air ingestion, and would also not build delivery pressure due to it. Did he mention if the suction side hoses were replaced? Nearly all are leaking by now if not.

74M35A2
Off topic : I pmed you about an alt & ac setup for my other A2 with an 8.3.

Back on topic
Fuel pickup was pulled & sweated just as a precaution.
All fuel lines have been replaced, removed & cleaned return check valve.
Ip is GETTING fuel, I did get it to start with idle stop adjusted.
I have some throttle linkage parts ordered now, will report when they are delivered & installed.
Im pretty sure WILLWagner hit the nail on the head with rack position & the idle was set with the throttle linkage & not the idle stop screw.

Again Thanks for everyone's help & suggestions.

Truck is not fixed yet but parts are ordered.
I will post the outcome when they arrive & are installed, should be in 7-10 days.

 

[WillWagner]

Any progress on this?