Starting problem, no throttle response below 5km/h most times. Good power at speeds

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Joined
Nov 2, 2025
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Location
Iceland
Need some advice from someone experienced in 90 cruisers.

I'm struggling with a really annoying problem that I can't fix for the life of me.
I've asked here before so maybe you'll be familiar with this a little.

This is a 99 year 90 cruiser not common rail.

The problem is that it takes a long time to start (10+ seconds) and when it starts it's at 400-500 rpm and doesn't respond to throttle or anything for a while. Usually after a few minutes it starts normally and is at normal rpm (830). After that you can drive it and it's good and has a lot of power, good response and everything except when it's fully warmed up then it goes completely haywire. Every time I go below about 10km/h the revs drop to 500 and it won't respond to throttle, so I either have to go to N and rev-match and then shift into drive. If that doesn't work I'm just stuck until it recovers which takes a different amount of time. Pressing the hand pump on the filter doesn't help. It starts quicker if I turn it off and on but it doesn't make much difference.

What I've done:
- Changed the oil pump 3x
- Changed the injectors
- Changed the oil housing (filter and hand pump) 2x
- All hoses to and from the tank.
- Glow plug and bracket there.
- most of the wires in the engine bay (either fixed or replaced)
- replaced most of the sensors (Tps, Turbo sensor, etc.)
- The time is 100% correct
- The time on the job is also 100% and I've tried changing it to no avail.
- ground is good everywhere
- tried 3 different computers
- All engine codes gone
- I've bled the entire system (using clear hoses and there's no air).

Please leave a comment or PM, I'd be very happy to get some advice, I'm really giving up as you can see, I've done quite a bit.
 
I had similar issues and found the diesel pump nuts was not properly tight.

I reset the pump on the timing mark and tightend both nuts on the pump down properly and all my issues was solved.
 
Have you checked the fuel pressure regulator? That sets fuel pressure that feeds the injection pump elements, and is also a check valve that keeps fuel from seeping back to the tank when shut down. If it's bad then the manual pump won't do anything.
 
I had similar issues and found the diesel pump nuts was not properly tight.

I reset the pump on the timing mark and tightend both nuts on the pump down properly and all my issues was solved.
Wow really, i literally have my pump hanging by 1 bolt, it feels super tight
 
Have you checked the fuel pressure regulator? That sets fuel pressure that feeds the injection pump elements, and is also a check valve that keeps fuel from seeping back to the tank when shut down. If it's bad then the manual pump won't do anything.
Have you checked the fuel pressure regulator? That sets fuel pressure that feeds the injection pump elements, and is also a check valve that keeps fuel from seeping back to the tank when shut down. If it's bad then the manual pump won't do anything.
WHere is this fuel pressure reg?
 
WHere is this fuel pressure reg?
I might be talking out of my bum on this one, apologies for that. Was speaking from experience with the 617, and your symptoms would match that.

Looks like the fuel pressure regulator is part of the boost compensator on these. My 617 wasn't boost compensated, not a system I'm familiar with.


Definitely talk to someone who knows more about this particular pump than I do before tearing into anything.

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