Quote:
Originally Posted by v8volvo
Still sounds like a possible inlet restriction or air leak but a sticky governor or intermittent sticking vane in the suction pump in the IP could be a possibility also.
Installing a clear section in the fuel return circuit as ngoma suggested is the best first step. If there is air present then that will cause these intermittent issues and then you just need to locate the source. For air ingress issues while running the only possibilities would be the driveshaft seal or between the fuel filter and the IP inlet. All other areas including the injector return circuit do not see suction when running and would not cause these issues so you can rule them out.
Just so that we are sure we are starting off with a correctly assembled fuel system, can you confirm these things also:
Fuel pump was installed using a dial indicator to set injection timing to correct spec including disengagement of cold start device while timing was being set? Any unusual engine noise or smoke when the power loss issues are occurring?
Fuel pump inlet and outlet banjo bolts are in their correct locations and not reversed? (Outlet banjo should be stamped "OUT")
New fuel filter was installed tightly and you are certain the old fuel filter's inner O-ring was removed prior to installing the new filter? The filters like to leave the inner O-ring on the filter head nipple and then when you install the new filter, it bottoms on the extra O-ring and the outer O-ring does not seal correctly. This can cause an intermittent air leak.
If these things are confirmed and you install a clear section in the return line and see no air in the return fuel during the problem episodes, here are steps to try next that will help find the issue:
1) Install a vacuum gauge inline between the fuel filter and the injection pump inlet. It is best to get some extra banjo fittings and fuel hose to do this rather than cutting the hard clear plastic line from the filter since that clear inlet line can be helpful. Run the gauge up onto the windshield or inside the car so you can watch the vacuum in the inlet line while driving. See what the vacuum measures when everything is running normally, then watch it closely when the problems are happening. If the vacuum reads much higher when the engine is malfunctioning, then you are dealing with an intermittent fuel inlet restriction somewhere. If the vacuum reading drops down when it malfunctions then that may indicate an intermittent issue with the IP's transfer pump. If the vacuum reading doesn't change then it would probably be another issue inside the pump. In any case this information will give you a direction to go.
2) If you can't get your hands on a gauge and fittings to do the above measurements easily, a quick alternative is to temporarily install a low pressure electric fuel pump (<10psi) inline before the fuel filter. If being fed fuel under positive pressure makes all the problems go away then you are most likely looking at an intermittent problem with the IP transfer pump. Unfortunately if the problems don't change by adding fuel pressure then you still will have the same list of other possibilities and will need to make measurements to figure out the next step. But with injection pumps that have sat unused for long periods of time, issues with the transfer pump are fairly common and can be intermittent. Fortunately if happens an intermittent problem can sometimes be resolved with ongoing use and letting the pump soak in some lubricant such as ATF.
3) Replace the fuel shutoff solenoid and plunger with known good parts or temporarily remove the plunger and spring to test. Problems with the solenoid are rare but if it gets weak or has intermittent poor contact then the plunger might not retract fully and create a restriction at the high pressure pump head. On rare occasions the rubber tip of the plunger can also come off and partially or intermittently plug the opening, but I have only had this happen once. As mentioned this is not a common trouble area so probably not worth looking at unless you do all the other diagnostic steps and still are not seeing the source of the problem.
Restrictions in the air intake, turbo, or exhaust could cause an inability to rev up but would be accompanied by a large amount of black exhaust smoke if they were bad enough to limit RPM this much. I would focus on the fuel system for now.
Good luck and let us know what you find out.
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Hey, thanks for the answer. This will help alot!
You typed so much that I can't really answer everything haha.
But now I know what to look for. I'm peacing together my other d24 so I can get it of my lift and out of my garage. So when that's done I'll start looking at this problem car of mine!
• What I can say this far is when the problem starts it comes quite a lot for gray smoke. Sounds normal but of course it cuts out on 3000rpm other than that no weird sounds.
• The banjos are correctly fitted.
• I have not installed the pump with a timer but I've done pump installs many times before the same way. Not the correct no but should still be working I think?
• I do not have a clear line on the fuel inlet since it's hard to find clear fuel line in sweden apparently.. I'll order some!
• no bubbles in the return line (return line is a clear line)
• it's a new seal on the driveshaft. My father installed it for me I can't really say. Maybe it could be damaged but he has done it loads of times.
The cold start device is unknown to me.. don't know how it works at all? The problem obviously occurs mostly on cold start.. should I try to re time the engine without the coldstart then?
This is as much as I know right now.. I'll check some more this weekend I hope
EDIT;
I havent done the vacuum test youre talking about, and I didn't really understand how to do it. Could you explain I another way? haha