1972 3.0csi Fuel injector pulse problem Help!

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BradCSI

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Hello,

Has any one had a similar experience.

I have nice 72 3.0 csi with 72k miles that ran fine until I changed to a after market fuel pump that delivers 42lb of presser and my problems began.

The car would not start, it was starving for fuel. I shot in a fuel source in the intake and the engine will run fine.

Here is a list of the things I have done to try and fine the issue:

1.Cleaned and tested lower trigger points and tested the points and found no problems.

2.Cleaned and tested all the grounds and connectors in the engine compartment, the rear seat area where the DJetronic box and the entire Djectronic harness.

3.Sent the Djetronic ECU box out for testing to a ECU builder that knows the unit well and it tested OK.

4.Tested the fuel rail for presser and test was good

5. I then tested the fuel injector harness with a fuel injector addnoid light, connected directly to the end of the fuel injector plug.

The test light would pulse 1 time with the starter going and did not pulse again until I pumped the accelerator, then I got a short weak pulses that would quickly fade to no pulse.

I plan to now move to the sensors. I was wondering if a faulty temperature sending unit could cause this problem ( possible telling the ECU to stop giving fuel because the ECU thanks its -200 degress out side.)

Any suggestions? Please help me if you can!
 
I have learned tha Open or shorted primary or secondary coils on the MPS sensor: Results in no injection pulses, the car is inoperable

I will test later today.
 
Fuel injection issues.

The fact that your pump produces less pressure than the stock pump caught my attention. If all you did was replace the pump, I do not see any direct causal connection to the vacuum pressure sending unit going south. But the pressure variation would cause me to x2 check the pressure to the injectors. As you undoubtedly know, with a couple of 10mm wrenches, the fuel pressure regulator can be adjusted (at least it has been adjustable on mine). You claim you tested the pressure which if too low, will cause poor running, and possibly even no running. I went through a number of those units that were "preset at the factory" only to find they didn't hold pressure.

I understand you suspect the vacuum pressure sender (see http://www.realoem.com/bmw/showparts.do?model=7031&mospid=47808&btnr=13_0733&hg=13&fg=15) to ensure we are speaking of the same thing. If it wont hold a vacuum, there is not much you can do. I tried soldering the bellows without success. But even if the unit is shot, I am informed there is a temporary work-around, I just don't know what it is. Person who told me about it said he got it from another site dealing specifically with DJetronics. I am guessing you can jury-rig the set screw to force the unit into a setting that may cause it to provide a steady signal for one speed. But again, that is a guess, and it would not be all that practical. It is also possible, that given that the part involves moving internals, something electronic has loosened up and needs to be resoldered. Unfortunately, the devices, so far as I am aware, are not designed to be torn apart easily, unless your name is Bosch. In any event, having checked out the brain, I would think it fairly easy to swap another pressure sending unit, and that would answer your question.

Another thought is a loose wire or bad ground problem. If, for example, the wiring from the pressure sensor is loose or has a break in it - you know the answer. Since all my wiring is brittle, I would probably go for a continuity tester, if swapping out the unit produces no result.

You also mentioned the temperature sensor/s. If you are speaking of the sensor in the manifold log, even if it is uncoupled, the ecu resorts to a rich default setting. Some folks evidently disconnect the sensor when they are unable to adjust the mixture and richen the same. As far as the other temperature sensor (near the auxiliary air valve on the side of the block) I think it pertains only to the cold start system, but I have not fiddled with this or even looked at mine for years -so I could easily be wrong.

All in all, I think the pressure sending unit is the likely culprit, having gone through a couple of them myself. But, there are obviously other little things that may be at fault.

I am sorry that this is not a given "fix", but perhaps someone else may be inspired to offer better advice. I have been in your shoes more that a couple of times and found it terribly frustrating.

Good luck and please keep us apprised of your progress!

Happy new year to you and all the other gluttons for punishment, er I mean coopsters!
 
THe D jet system ECU is pretty robust so I doubt if thats the problem
Now from memory the fuel pressure rail should be set at 28 lbs.
The air temperature sensor and the coolant temperature sensor are pretty reliable so I doubt if they have gone.
It seems strange that just by replacing the pump you have ended up with these problems. What makes me concerned is that you state that by squiting fuel in the inlet it runs.
This would make me suspect the fuel side of things including the new pump. Sorry to ask the obvious but

1... Disconnecting the fuel line at the engine does the pump deliver fuel?
2... No kinked or crushed hoses?
3... All D jet connections clean and made?
4... Fuel return line ok?
5... Punp "running" the right way round ie inlet and outlet correct?

HTH
Malc
 
D-Jet Problem

Thank you all for the replys

This issue is frustrating.

The problem is not in fuel delivery system. I checked 1 through 4 and seem in good order.

The presser regulator could be a problem, but unlikly.


The problem seems to be isolated to the electric spark that is sent from the lower points in the distributor to the injectors via the injector harness. There is no electric signal telling the injectors to fire. I tested using a light pluged on to the injector plugs on the wiring harness. There is a very weak to no spark signal action going to the injectors.

I inspected the points they looked ok, but I am planning on putting a new set in.


Disconnecting the fuel line at the engine does the pump deliver fuel?
2... No kinked or crushed hoses?
3... All D jet connections clean and made?
4... Fuel return line ok?
5... Punp "running" the right way round ie inlet and outlet correct?
 
Could be the FI points. I would also suggest you carefully check the wiring from the lower set of points back to the ECU. In fact the whole injection harness a tedious job but probbably worth it. Look for dirty and cracked wiring. A good multimeter is a worth while investment at this point.
Malc
 
Have you confirmed you have correct fuel pressure to the fuel rail? And, have you cleaned any possible contamination from inside th fuel rail?

If the current from the lower points to the injectors is weak, perhaps the wiring is to blame. 30 year old wires can cause a lot of resistance, fresh wires could put you back in business.

And I am definitely working without a net here v-a-v my d-jet knowledge, but it seems unlikely that the signal from the points drives the injectors directly. I'd expect that the points are a signal to the ECU, and the ECU fires the injectors.
 
Your correct the points do not trigger the injectors, they are basically a "sensor" to tell the ECU when to fire the injectors.
Malc
 
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