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Injector pump damage?


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1987 Superliner w/e9.  Engine was running fine.  It sat for a couple of years and the clutch was stuck.  I pulled it into gear and it moved forward and stalled.  Now, it won't start.  Acts just like the fuel shut off is closed.  Could the injector pump be damaged?   Any ideas are appreciated.   Thanks  

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On the inline mechanical engines I've heard the fuel rack can get sticky from sitting. If you disconnect the fuel shutoff linkage from the lever, does it have any resistance? I'm just guessing, I've never worked on an e9 nor do I know how the fuel pumps function compared to inlines.

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Mine has the "V" injector pump.  I did stroke the fuel shut-off lever, and it is normal. 

The motor cranks normally.  It just acts like it's not getting any fuel, which it isn't.  I was thinking the drive gear to the injector pump may be damaged, or something else inside the pump shifted.  The starter can move the truck easily, which makes me think there's no mechanical damage.   The hand primer pump doesn't seem to circulate back to the tank freely now.  Any thoughts?   I thank you for your reply. 

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Is there any kind of electrical shut-off for the fuel transfer pump?  I'll check out all y'alls tips.  When the motor lugged down to stall, could it have turned the injector pump backwards?   There may be a check valve right at the pump.  It's a little wet with fuel now.  Maybe forced shut to hard.  I'll look it over Friday.   Thanks again!

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Get a nut at any injection line loose. Crank the engine. You you should see fuel pulsating from under the nut. If it's there the plunger in the pump operates. You may check all 8 of them. If no fuel pressure in the injection line there may be a boquette of issues including prime or air or rack locked in the shut-off position or others.

Никогда не бывает слишком много грузовиков! leversole 11.2012

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19 hours ago, bwdozerman said:

The throttle shaft turns OK.  Maybe it can disengage from the rack.  I'll loosen a few injector line nuts, but, don't expect to see fuel.  Everything seems fine, except no fuel into engine. 

Take the fuel line off at the inlet to the pump crank the engine and see if fuel is coming to the pump! if there is no fuel you have a supply issue !  

Also check out my post in odds and ends  V8 Therapy! just an odd ball failure ! The engine just up and quit !  It can happen ! If you got fuel to the pump and the rack is ok! U may need to check the timing ! If you eliminate all the other options posted here post and I can walk you thru the steps to check this failure It is quite simple!

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  • 2 weeks later...

Are the screw caps that expose the fuel rack on either side of the timing cover?   The tachometer is connected to one of them.

The throttle lever pivots freely, but, doesn't appear to be moving anything internal.  Stopped by the Mack store to try and get an exploded parts view, but, they couldn't get anything off their system.

I haven't actually opened anything, just took the photos below.   The fuel inlet has the silver fitting, mabe a check valve. 

Let me know what to open to expose the fuel rack.  Thanks, 

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Long cap is puff limiter which limits rack travel until certain amount of boost from intake  

Tack is down in front between air comp n steering pump 

that fitting is return check valve is in pump or should be 

if it was me i would give it a good wash before taking anything apart

Edited by Back In Black Pulling
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I cleaned up the area and remove both screw caps and the timing cover.  Rack moves freely.  Pulls all the way in when fuel shutoff lever is rotated to shutoff position, and pushes out when throttle lever is rotated.

The hand primer lifts fuel easily through the filters.  After cranking to start, it seems like the hand primer pressure is lower.  There is no external lift pump on my truck, that I can see.  Is there a way to check the low pressure lift pump section of the Ambac pump?  Maybe it's something else.   Thanks, 

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I removed the fuel return check valve.  It shuts off good and has appropriate spring back pressure. 

I will try the ether like you suggested.  There is no smoke at all when cranking, making the fuel supply issue likely. 

Please say exactly where the fuel lift pump is located.   I was thinking it was inside the injector pump, like a farm tractor.  Thanks, 

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3 hours ago, bwdozerman said:

I removed the fuel return check valve.  It shuts off good and has appropriate spring back pressure. 

I will try the ether like you suggested.  There is no smoke at all when cranking, making the fuel supply issue likely. 

Please say exactly where the fuel lift pump is located.   I was thinking it was inside the injector pump, like a farm tractor.  Thanks, 

Should be able to follow fuel lines to see where lift pump is, terry:MackLogo:

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On 6/19/2023 at 6:31 AM, bwdozerman said:

I cleaned up the area and remove both screw caps and the timing cover.  Rack moves freely.  Pulls all the way in when fuel shutoff lever is rotated to shutoff position, and pushes out when throttle lever is rotated.

The hand primer lifts fuel easily through the filters.  After cranking to start, it seems like the hand primer pressure is lower.  There is no external lift pump on my truck, that I can see.  Is there a way to check the low pressure lift pump section of the Ambac pump?  Maybe it's something else.   Thanks, 

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bar the engine over till you see the hole in the adjustment hub  in front of the gear on the pump dead center in that opening and then check to see if the timing marks are any where close to the pointer! if the timing is within the numbers on the damper your timing is close enough to run 17 -24 ish! if the timing marks arn't close pull the compressor and and check the gear same with the power steering pump!

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Timing checked out to be ~19 to 20.

Hand primer pumped up tight, but, no return flow to the tank.  No return flow to the tank while cranking either. 

Removed lines to lift pump.  Very obvious that no fuel at all is passing through the pump.  I don't have any idea of how the passage from inlet to outlet works.  Most likely springs set to control precise pressures.   Something must be seized to prevent all flow.  I turned the motor with a bar and the pump gears do turn.

What's the best repair strategy?   If I go to the Mack store, they'll most likely not be able to look up or supply a replacement.   Thanks again, 

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 The Mack store will give you a blank stair unless you happen to run across a parts man in a wheel chair and hearing aids ! 🤣 Appears to me someone has put in an extra check valve on the fuel return under the stop lever there ? remove that number 6 line fuel should flow when you pump the primer up! The other thing is stick your finger in the hole where the pump came from  and feel around in there I have seen this idler gear fall off ! it is held on by a c clip! it runs off the governor drive! I have also seen this gears idler shaft so worn the gear flops around a lot I would usually check this if I have a pump off as you have there! I really  sounds to me like you got a restriction on the inlet side from the tank! By what your describing! 

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