I have a 76 914 that's been in my barn for 10 years. Trying to get it running again. I’ve searched this forum and other forums and the internet extensively, and can’t find an answer, or don’t recognize it!
My questions are:
1: Can bad or maladjusted trigger points shut down 3 injectors and allow one to work?
2: If the throttle switch, when throttle is stroked, cycles one injector about 20 times, shouldn’t it make all injectors click? Just one does.
3: Does the throttle switch bypass the Control Unit or at least the computing in the Control Unit?

What I’ve done so far:
Sprayed gasoline into the throttle body. Ignition system and timing work – thing runs and sounds good.
The relay board and sockets needed cleaning, and I got the relays working so the Fuel Pump and control module have power as I’ve read they should. Fuel pump runs a few second when key is turned on. Pressure is about 30 psi.
I’ve also read that moving the throttle (and switch) should, cause the injectors to “click”). Only #4 cylinder injector does anything.
I then re-did the grounds and rang out the wires to all injectors - grounds to ground and power wires to appropriate connections on the Control Unit - all had continuity.
I took the injectors out and sure enough, only #4 sprays gasoline. If I move the #4 wires to another injector, it works, so only #4 connector is getting a signal and at least one other injector will work if it had a signal.
The rest won't even click. I tried a different control unit – same symptoms and only #4 injector doing anything!
I'm thinking of trigger points, but if they are bad/misadjusted, a pair of cylinders would fail instead of three, wouldn't they? And bad trigger points wouldn't keep the throttle switch from cycling all four injectors, would it?
Thanks for any ideas or guidance. I’m about frustrated and out of ideas. Maybe a little a little dynamite………………………….

Gordon

All of the fuel injectors ground at the center of the engine near the transmission at the top. It is a multiblade spade connection and a group of white wires goes to it. They could easily have come loose and not be grounded. I would check this first. The good news is that your injectors work. The trigger points do not pulse each injector individually, the brain does this in pairs, so the wiring between the brain and the injectors is by far the most likely target.

Try ringing out the wiring harness to the CPU connector.

Also -admins this time I think I am correct -

Mark,

I have checked them out - each injector to it's CPU contact (3,4,5,6). When all else fails, do it again and again and again - darn!

Thanks for the reply!

Gordon

Worn,

I took that apart and polished the bell housing, nut, bolt and connectors.
No change,ordon but I'll do it again !

Thanks for the reply.

Gordon

I have a 75 d-jet, and had similar issue, been afew years so i am trying to remember the remedy, i did have to replace my CHT and my MPS unit, but wires to the injectors were not making contact. -
if it is the trigger points or one set of grounds you will fire 2 not four, not just one.
keep working thru the injector circuits and wiring, that has to be the issue.

It could be multiple problems adding to each other, which makes for even bigger headaches.

The trigger points run pairs of injectors, on the diagonals. I believe that's #1 paired with #4, and #2 paired with #3.

I believe the grounds are paired with the lefts together and the rights together.

Debris in the fuel tends to affect the right-side injectors first, because they're closest to the supply.

The "accelerator enrichment", I think, only activates whatever injector pairs are currently selected by the trigger points.

The injectors are always grounded. The ECU supplies them with voltage to get them to open. Does every injector connector have a good solid ground on one wire? Does it intermittently have voltage on the other wire? A "noid light" plugged into those two wires can tell you if there's electrical signal or not.

http://members.rennlist.com/pbanders contains pretty much everything that anyone knows about D-jetronic EFI these days. Read through it and take in as much as you can.

--DD

Dave, Phil and all others, thanks for the replies.

Dave, while a newbe on this forum, I used several forums 10 or so years ago, and always valued your advice. I'm sure there are others in this forum that have great info too. Today, I put in an alternative '74 harness and now two injectors fire (increased by one!). Makes me think the harnesses are the issue.

I think I read somewhere that the throttle switch "clicks" the injectors up to 20 times per throttle travel and therefore provides "accelerator" pump function?

I've heard of a "noid light". What are they and can I make one? What is the voltage to the injectors?

The two injectors that now fire are both on the pass side, so doesn't seem like the trigger points.

I'm wondering if the stabs in the CPU and the harnesses are dirty. I'm going to take a pencil eraser and clean them. If I have a noid light, I may strip a little of the old harness near the CPU and see if a signal is coming out.

There appear to be firm grounds on one wire on all injectors. I'll check the grounds again on the drivers side, since they are not injecting.

Thanks again, Gordon



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Sounds like you are making progress. Check with Jeff Bowlsby. He rebuilds harnesses. I was chasing my tail and eventually just pulled the trigger on that and got new harnesses from him an f.I. harness and an ignition harness. Or you can send him yours, he will test it thoroughly and fix all connectors and replace what is not working etc.

A lot of guys will give up on these injection systems but they are not that complicated And since it is all sorted out you will get better mpg, performance than with carbs. ( that comment will open up a can of worms)
Actually they both have their issues. But I have been happy now with my performance .,

Got this figured out I think! Finally found, after swapping control modules and wiring harnesses several times, two of my injectors wouldn't "click" no mater where they were. Also, the trigger points won't let more than two (diagonal) injectors fire at once, so my testing wasn't making sense. I thought I was getting no signal, but signal was there sometimes, but injector was bad. Other times, injectors wouldn't fie 'cause trigger points were lined up for other two injectors....

Unfortunately my set of injectors that click have been attacked by mud dabbers over the years, so guess I'll have a set rebuilt. I can figure THAT out I think.

Thanks for all the ideas.
Gordon

Malpais82e,
What was the final resolution to this problem? My wife's 914 is now doing the exact thing yours started out doing. The only injector that clicks with the throttle switch is number 2. Number 3 does not click when number 2 is clicking which it should because the trigger points are the same for numbers 2 & 3. When I turn the engine 180 degrees onto the other side of the trigger points neither numbers 1 nor number 4 make any clicking noise when the throttle switch is moved. I had the injectors cleaned, tested, and flowed by Marren Fuel injection so I really don't think that the injectors are the issue.

The harness when I had it out of the car was rebuilt by my self and all of the wires tested correct for continuity I replaced any damaged boots and harness ends. I'm left with the belief that the injector points are bad on the 1-4 side, and the grounds are not connected securely on the 3-4 circuit.

But since they were acting the same I thought I'd ask what you found?
Thank you