Yesterday was my final straw at trying to resolve my sporadic engine stalling issues. Over the past few months I have been replacing various components in an effort to resolve my intermittent engine runnability. The primary focus had been coil, wiring, distributor and ignition parts. Thanks to many helpful tip from this site I narrowed the problem down to the fuel pump not getting current on occasion. My relays seemed OK so I thought the problem might be coming from the ECU occasionally thinking the engine RPMs had dropped below 100. My understanding is that this is fuel cut out is to prevent some engine issue. Using my volt/ohm meter in the cockpit as pictured I attached a lead to Pin 3 on the relay board to see if the ECU would occasionally drop the ground on the fuel pump relay circuit. To my confusion I was getting erratic measurements as I took a ride down the street. The car was bucking and surging and stalling. About a mile away from home my intermittent running issue became a full-time problem. I could activate the fuel pump as I turned the key just like it is designed to do but once the starter engaged the engine only ran for a few seconds apparently from the initial fuel pressurization but the that was all she wrote.

I limped home and it looks like by hot wiring the fuel pump I will be able to drive it to a local import car shop that has a mechanic familiar with D Jet systems. Despite my frustrations and throwing in the DIY towel, I am glad that this problem is continuous which should make it easier fix.

I will post what it took to resolve this problem once I get it back. My shop appointment is 3 weeks out yet....

You gave it the ol' college try. Good for you for handing it over to someone else to puzzle out.

Your fuel pump issue could be as simple as a bad ground wire, maybe try that...

Please keep giving this the college try. It's fixable! I honor those who decide to fix it rather than swap to carbs or some other cop out. The answer is usually simple. Some just give up and swap. They lose. There is an answer.

When you say erratic measurements, what were you seeing? Normal operation is pin 3 would be zero volts. Keep in mind that a VOM has a hard time following a moving signal and will display all kinds of numbers. Sounds like the ECU is dropping pin 3 and cutting out the fuel pump. I assume you checked the contacts on the distributor? The ECU has no idea how fast the engine is turning thus needs the contacts to operate.



If you hot wire the fuel pump, how does the car run? I'm with Rand; keep at it and you will find the issue. I don't like giving up on an issue. Being an engineer who's job is to debug boards/systems I can't give up.

You have 3 weeks to keep trying with a backstop on the horizon - keep at it!

If you could build a time machine
And go back in time when people knew how to work on fi
And parts were available then youd be all set

Wondering if an intermittant short is the issue by chance?

I went to carbs many years ago, and after experiencing the lack of performance and drivability issues with carburation, I went back to original FI, sorted it out, and have had a great running car since.

I rarely repeat myself because, hey, I gave you my advice and it's your choice whether to use it not*. But...


You are incorrect. Except for the ECU turning off the fuel pump when it is not seeing spark at the coil, there is no magical "oh, there's a problem, turn off the fuel pump" logic in the ECU.

If all wiring is solid, and the engine is turning resulting in the coil creating spark, the ECU will keep the fuel pump on.



...indicating that you have a fuel pump and/or distributor wiring problem.



Indicating you have a wiring problem.

Thus, allow me to be redundant and repeat myself (but I digress). See Post #8 in the other thread. Can't speak for Jeff's Post #10 follow up (I've never used it) but you should consider it.

If nothing else, let the mechanic know this so you aren't spending $125/hr for someone to diagnose a wiring problem (in this case, collapsed and/or corroded male pins at the replay plate and/or relay and/or a bad relay plate that are causing intermittent electrical connection.)

Good luck and let us know how it works out!


*That's become my career mantra. I used to get all upset and follow up later with "Hey, I told you so" but that proved to be career-limiting. Now it's "here's my advice" and then let them go their own way. They can use that all they want, no matter how they hold their hands while declaring it.

They found it ! My intermittent running issue has finally been solved ! My local repair shop worked on my issue for about two hours and determined that my engine would sporadically shut down due to a poor ground connection inside the ECU. The problem was fixed by using another ECU that I had recently obtained for one of our members. I can only say thanks to all who helped try and guide me through this problem. I now am looking forward to some fun drives through town with the top down and the radio blaring.

Amen, all's well that ends well.

Now enjoy!!!

Vysoc

Good to hear, thanks for letting us know what it was and that you are back on the road.

Can the ground inside the original ECU be fixed, to carry as a back up? - 'cause remember the new ECU is still 45 years old!, with a chance of the same.

Fantastic! Hopefully the "old" one can be repaired and used elsewhere.

Carburetors were used with great success on automobile and airplane engines for decades prior to fuel injection. Utilizing a tried and proven method to get gas into your cylinders is hardly a "cop out". My twin Dellortos work just fine, and they do not present head-scratching, unsolvable problems, when something does go wrong. I guess this argument will go on ad infinitum.

Ansbacher