Kirbert asks…
So, what are the chances that replacing those two transistors would restore function in an ECU that’s holding one bank on?
I think for resolving our poster’s problem, the real question is what is the probability the ECU is faulty ?
So, how many circuits are involved to keep 6 injectors off for Bank A, and six injectors on for Bank B ?
Each bank having 2 groups of three injectors each. Each group requiring a HOLD circuit and each group requiring an ON circuit. I get eight (8) circuits total.
If transistors are at fault in the ECU, which two groups have the faulty transistors, and are the faulty transistors holding the injectors ON or not operating the injectors ? And depending on that answer, what then is the problem with the other two groups of injectors on the other bank, (the B bank) that don’t operate at all ? Exactly the opposite problem. Is that broken wiring on two groups of injectors ?
And can four of the circuits be discarded because the resistor pack has been tested as good ?
Jim Brighton… Where are you ? You post suggests you might be the electronics guy with the answer.
SD, I tried two ecus yesterday. The 6cu holds bank A on and the 16cu does nothing, maybe a flicker on bank b every so often. If the injector wiring isn’t at least part of the problem I will be very very shocked. I’ve got the parts I need to rebuild the harness ordered( I thought I had them but I had the wrong connectors).
electrickery is not my strong suite. If i had a questionable four wire harness I would use my VOM for continuity and resistance. but, double up on light bulb test. Will each wire complete a simple light circuit. Bright and steady wins. Dim, dark or shaky loses.
Agreed, that wiring has seen better days for sure.
Here’s my opinion and only an opinion, you’re questioning the engine the ECU and everything else before dealing with the fundamentals. You should replace (rebuild) that injector wiring harness, also whilst you’re in there you should have a look at those injectors, hoses and fuel rail and have them serviced. Just looking at the corrosion on your ferrules on your fuel injector hoses they haven’t been touched. Your injectors need cleaning, servicing and flow testing.
Dave (SD Faircloth) is too much of a gentleman but I’ll give him a shameless plug. Send your fuel injectors to him and get it sorted. I did that in my car and it has run great ever since. You don’t want one of your cylinders running lean or it will give a you a bad day
My two cents.
1 Like
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
47
We should probably put a subforum on here for slot cars!
Well…forgive me…but now I need to jump in here and maybe give some folks a little injector lesson. Andy…do not take offense ! Not meant in any derogatory sense, or aimed at you personally. The word “rebuild” for injectors is thrown around a bit too carelessly. You cannot rebuild an injector. You can maybe rebuild an alternator. Pull it apart, replace some electronic parts, etc, etc and put it back together and test it You can rebuild an engine…tear it down…etc.etc replace parts, machine parts, put it back together and test it. But, you CANNOT rebuild an injector. You cannot take it apart, pull the coil, pintle, etc out of the body of the injector and buy replacement parts to put back in. Well, maybe you could but nobody does that. No injector shops do it. No individual does it. Nobody sells new coils, or a new pintle assembly. Why ? Because the tolerences are too small. Micron measurements between the injector pintle and the pintle seat. Millisecond operation time for the coil. Nobody has the $$ required for a machine to do that. Well, the mfg’s do. Most folks don’t have a machine that you can flow test an injector after you replaced parts (if you could by parts) to verify your work. To verify flows, to verify opening/closing times, etc.
The only thing most laypersons can do with an injector is to replace the filter and the pintle cap, and the seal. Only the filter replacement may help with an improper flowing injector…if it’s clogged with crud from the tank. The other two items, do absolutely nothing to improve an injector flow or operation, or stop a leaky injector, or improve a spray pattern. The pintle cap doesn’t control the injector spray pattern. The pintle cap protects the pintle from damage. If the pintle gets bent or sheared off from mishandling, the injector is toast. Throw it in the can. The ultrasonic cleaning, and tank additives may/will clean injector pintles and the seats, but you need a pretty respectable device to actually measure the results…quantitatively. The measuring of flows is the only real quantitative, definitive test to prove if any cleaning method worked, be it ultrasonics or otherwise. There are a few folks here who have devised homemade flow devices to measure injector flows. Not knocking those efforts, but they are rather rudimentary, but you do get an A for effort.
One micron is one millionth of a meter. The injector filters on the V12 engines catch particles at the micron level. Right at the 10 micron or larger particles filtered out. Smaller than that, and particles pass thru the filter, into the injector and usually out thru the space created when the injector pintle lifts off the pintle seat. So…think 10 microns. Pull out one hair from your head…that’s about 70 microns in diameter…give or take. Now split it 7 times and that’s where we are with injector tolerences.
Forgive my long windedness. I hope this helped. SD Faircloth
Thank you for sharing your professional expertise. I also thank your for your technical articles posted on your Jaguarfuelinjectorservice website. I’ve learned a lot from them.
Adam,
The following post with wiring diagram from BobPhx was one of many posts after your original "Fuel dripping . . . . " post in August 2021.
Note that the injectors fire in groups of three, if you trace the harness you’ll find one wire servicing 3 injectors.
Somehow I thought you already rebuilt or rewired your injector harness.
They are a constant source of faults on older cars and will always be mentioned by forum members when an engine fault concerns injector operation.
It is now January 2022 and it looks like you still have the old harness which is a mess as expected.
The photo looks as if there are lengths of concertina type plastic tubing over parts of the wiring.
That was not original and might hide “fixes”.
This may or may not be the total source of the fault you mention, or it may be PART of the fault.
No matter, it should have been fixed before because many posters have tried to help you but you but you are not being systematic.
Now we are in the dark. I did ask a question earlier about what was the outcome of trying the other 2 ECUs. You did not answer which is a pity because it could have eliminated the possibility your original ECU was faulty.
It is important to read the comments from posters trying to help you and if there are questions raised do not ignore them. Try to answer the questions and that helps posters zero in on the most likely answer to the problem.
At this stage all bets are off. All the suggestions from posters do not mean much because you have an engine with a useless harness. If any of the “low” side injector wiring was shorted to a +12V wire in that harness that might blow up one or more transistors in any of the ECUs connected to the harness as soon as the engine was cranked.
Where to from here ?
First fix the harness. The injector connectors are usually called Junior Timer plugs, note some have an extended wire retainer, some don’t. Make sure you buy the right one They are easy to find with crimps and boots to go with them. Buy extra crimps, you will need them and they should be cheap. Follow the wiring diagram. Looks like the colour on the plug matches one of the stripes in the wires to the injectors. If you are not sure, ask for clarification. To speed up diagnosis you could use any suitable wire, maybe red for +12V and black for every thing else and cobble together a temporary harness from the original 8 pin plug to the injectors. Wire length not critical. Use cheap plastic terminal blocks where you need to junction wires. Keep wires away from ignition circuits but otherwise anything goes. You will need a tool to put crimps on the wires, and any auto store has them.
The idea is to get something fixed up that is wired 100% correct. You can always make a pretty harness later when the engine is working.
Then we start again trying to help you get this car mobile. We all like Jags, especially the XJ-S, and we all want you to succeed. Report what you see or find when you next try to start the engine. Carefully check comments or questions from posters and make sure you answer them as best you can.
2 Likes
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
55
I appreciate the information. I cleaned them in the ultrasonic cleaner and replaced what I could on them. Pintle caps and seals etc. I don’t have the equipment to test them so I used an archaic method with hose, brake cleaner and my power probe. They aren’t leaking and open and close with voltage. If they turn out to be a problem, I’ll send them to you for a rebuild.
In fairness, this forum is insanely helpful and responses come in fast and abundant. If I didn’t answer a question it’s because I didn’t see it posted. The harness will be rebuilt by next weekend after my parts come in. I’ll report back what happens after that. If the ecus got fried then I have to deal with that. If I have to buy another ecu then I will. Spark plugs and wires will be replaced while I have the valley exposed. I should probably repair any other old wires I see as well. Also the vacuum advance broke in half on the distributor by me touching it. I’m hoping that isn’t too difficult to repair.
Not leaking and operating is good. For the moment, set those aside as not the primary source of your fueling issue. Getting the injection harness rebuild will be a major step to getting your vehicle operational. Keep at it. SD
