BJ40 1979 Erratic Acceleration after full engine rebuild (1 Viewer)

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Recently had the engine of my BJ rebuilt (for the 2nd time). Have been testing it for a few weeks. If I am just driving around town there is no noticeable issue. But after about 40 minutes of use, the acceleration gets very erratic... I could be going along a flat road in 4th and the speed starts to decrease even with the pedal to the floor, change to third, still no acceleration, down to 2nd... still the same... then suddenly it will pick up acceleration again. When this happens on a hill, dropping to first gear, the car does not accelerate and has now stalled twice. Then it will drive normally for about 10 minutes or so before the problem starts again. It only seems to happen when the engine is warmed up and has been in use for more than 30 minutes, if I just drive for 10 or 15 minutes there is never a problem. In addition to the full engine rebuild, I have had the fuel tank and lines cleared, new fuel filter, new injectors, air, and oil filter. Any ideas where to start looking? Also, there is a big plume of white smoke when starting the engine, even when the engine is warm. Thanks, Jules
 
Sounds like a fuel pressure issue. I’m assuming it’s diesel. I have no experience with small diesel motors only the large ones in our heavy equipment. Erratic motor is usually a fuel blockage or pressure issue, can be air but it wouldn’t want to start cleanly if air was present.
 
hi,
i think that you have a b motor

normaly it's a little black smoke when you start your motor
small smoke white = problem water or oil

you have a pipe on side of your motor, have you a big smoke at the ouput of this pipe?
at the input of the manuel fuel pump (feed pump), you have also a filter number 22

20190914_192310[1].jpg
 
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Its definitely a fuel issue. It's most likely either sucking air, a restriction, or a lift pump failure:

A few things to check:
  • If there's a sedimenter fitted, bypass it. Factory sedimenters are a common source of air and blockage. You can refit an after-market one if it turns out to the be the problem. It may be bolted to your left hand side chassis rail if its fitted.
  • Check all of the fuel banjos have crush washers fitted. Given your engine has just been rebuilt its probable that many of the banjos have recently been undone. New copper/aluminium crush washers should have been used on re-assembly. Banjos have crush washers either side of the fitting. There are banjos at the
    • lift pump inlet
    • lift pump outlet
    • fuel filter inlet
    • fuel filter out
    • injection pump inlet
  • Check the flexible injector return line hose is in good order and securely clamped in place at each end
  • Check that the rigid injector return line wasn't damaged when removed/re-installed
  • Replace the fuel filter if it hasnt been done recently
  • Remove the lift pump from the side of the injection pump and check that when its pressed in that it springs back. Disassemble and clean whilst you have it off and replace the 4 crush washers when reinstalling
  • Check all flexible fuel hose for cracks or poor condition
Also, check that the two hoses coming down from the throttle body to the governor housing on the injection pump are in place.. if these are broken or not in place you'll have poor throttle response. Unlikely given the symptoms you've described - but worth a check.

Its often not easy to find where air is getting in.. mostly I just work my way back from the pump renewing and/or inspecting all components of the fuel delivery system.

Here's what is often found inside the factory sedimenter..

1568329782133.png

Here is a short video I made of what a failed lift pump looks like, whilst its off a 2H the B series engines have the same lift pump fitted.

 
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when this engine has been rebuilt is that the rating of the overtaking on the 4 engine liner has been properly controll ?



20190914_192146[1].jpg


20190914_192146[1].jpg
 
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