After completing an extensive preventative maintenance project on the car it ran great for about 20 miles. It suddenly started missing and within 5 miles it was barely running. When I can get it started and running the plugs become very black and sooted up in a few minuets.The following items have been checked, tested and tried to get it running again.
1. Tested coolant temp sender, air temp sender, MPS. All check OK.
2. Test lite on all injector harness terminals. All are getting voltage to fire.
3. Ignition system is providing a good spark.
4. Replaced Trigger Board.
5. Fuel delivery system working well. Filter on suction from tanks and just before fuel rails. Pressure good @ 30PSI.
6. Pulled plugs on all FI harnesses and cleaned terminals.
7. Injector wiring harness is fairly new and in very good condition.
8. All injectors cleaned and tested.
If it starts you can barely keep it running with the throttle. After a short time of running the plugs become very black and sooted up. Have pulled & cleaned plugs several times and they all become sooted again very quickly.

What can be going on in all combustion chambers to cause this?

 

All plugs sooty? That would be rich. Try unplugging the cold start injector and remove it and make sure its not leaking fuel into the manifold. Make sure you have at the vacuum based load sensor (MPS) on the front radiator support. Common for the the T fitting to crack or one side to come off.

When you say "1. Tested coolant temp sender, air temp sender, MPS. All check OK." how exactly did you determine the are ok?"

You should use an ohm meter and the resistance should change based on temperature. You also may want to get a wiring diagram and check for proper readings at the ECU to eliminate the possibility of a broken wire.

 

Another thing would be to check the wiring harness that connects at the back of the throttle tower is in place (They like to come out and are covered by a rubber boot, so you cant see its fell out)

+1 on the cold start injectors. I deleted mine and it starts a treat without them (albeit thats a California "cold start" and not a Nebraska cold start)

Did you replace the fuel injection trigger board with a 4 wire version ? (or did yours already have that)

As there has been a lot of work done (in all the right areas for this engine) and it did run great for a bit, I suspect something "silly" has came off (wire, vacuum hose) I would look around the engine bay very carefully to see if something has come adrift during the good efforts of preventive maintenance.

 

1. All plugs are sooty in less than a minute or less of rough running. Although black and sooty, they are not wet.
2. No difference with cold start injectors removed.
3. All component resistance tests done with ohm meter and checked OK according to temp.
4. MPS held vacuum.
5. 4 wire trigger board installed.
6. Also tested and adjusted throttle switch.
7. Have looked many times for unhooked wires or hoses, etc. Can not find any.
8. What would be procedure for checking wires from ECU?

 

If its that sooty it is overfueling and attempting to burn it off.

FPR's fail on these, and that will cause it. There is no vac attachment as in the HE. The diaphragm splits, you still get a pressure reading on the gauge, but raw fuel is by-passing. You dont need much raw fuel to soot up a PreHE.

Our PreHE will soot up at 30psi. I run it at 28.5 ish, and it is sweet. I set the FPR's at 30, then use my ear to fine tune them. These PreHE's are a mongrel with overfuel.

Unplug the fuel return line, extend it over the fender into a container, try it again. That return pipe and hoses/fittings/valves may not be allowing return fuel to the tank/s, and that will do the same.

Look under the car, near the front LH jacking point. There is the return pipe, and I see many damaged due to workshops not using the jacking point and crushing that pipe.

I'll keep thinking and come back later,

 

When Our xjc "sarc" was having those issues it deff was fuel related.
also at idle it would run awful.
I ended up adjusting the knob on the fuel ECU in the trunk all the way around, it clicks so you can see where u are at.
the throttle pot needs to be set perfectly at the idle spot or that will not work and it wont think its in idle mode.


Another thing I tried "as a diag" was with the coolant temp for the fuel injection. If you remove the plug, and "while engine is off with key in "on" turn the throttle and you can really hear there injectors clicking loud. that's full fuel right there. start the car see how it runs for a sec.


Then I shorted the plug with a wire and did the same thing and the injectors were really quite "less fuel" and it ran nice.


all this might help in some further of finding out where the issues is.

 

Thanks for the suggestions.

In my recent project on the car the whole fuel supply system was redone including new fuel pressure regulators. The engine ran fine for 20-25 miles. There is no obstruction on the return lines. I have a gage attached to the supply to the left cold start valve. I have adjusted both regulators to 29-30PSI. It ran fine when first back on the road. Do you think a FPR would go bad after only 25 miles? How would one check to see if one was bad without putting in new ones?

 

this is precisley why i went to a standalone injection system on my V12!

i just didnot want to screw around with the old Bosch stuff, hunting parts and more.

12 new injectors also. i now run 45psi F/P,adjustable, much finer/atomized spray patterns

 

Now I seriously doubt the FPR's.

Somehow that thing is overfueling.

The cold starts are already mentioned, and yes, I remove them 100%, even on the HE.

The throttle switch, maybe, but usually it gives a stumble off idle.

Just because, is the spark a nice fat Blue, or is it a dull Yellowish. That original Opus ballast is a nightmare now due to age.

The coil on these is nothing special, just a "ballast" spec coil, and sometimes a non ballast coil gets in there, and with the 7V it runs on will not give a "fat" enough spark. Conversely, if that ballast coil gets a 12v supply at "run time" , due to ballast issues, it will only last a short time before going crappy and then legs up.

I replaced that double injector rail nonsense on one with the HE square rail and just used 1 FPR on the LH side, which is the outlet. Really sorted some strange issues with that engine. That FPR was set at 28psi.

 

The Opus ignition has been replaced with a Crane XR700 system some time ago on my car. I have checked the ballast resistor. It is OK. I have swapped in several good coils, another Crane amplifer and installed a new trigger board, all with no help. The over rich condition didn't change. The spark when starting is very good. I don't know how to check if spark is good when in run status, but with all ignition components checking good, I assume it is OK. I am running out of things to check. I can't find any grounds that look suspicous. I would like to check the continuity of all wires from the ECU, but I am having trouble finding their termination in the engine bay. I suppose next would be to try and find a good ECU to try.

 

is it possible that dirty injectors are holding open, and spraying fuel constantly?

 

Possible... But surely not EVERY injector is like this, and if they were, no doubt she would only run for a couple seconds before flooding.

Silly question, but are you sure the ATS and CTS haven't been accidentally swapped?

 

Somewhere in my thousands of paper bits I have a wiring schematics for the PreHE.

I will go look today sometime and see if I can find it, and post back tonight.

What ballast are you using?, The Opus unit I am assuming.

I did that on Sir Arthur, oops, went for a more conventional set up, and had the Tacho altered for coil pulse instead of the original ballast pulse.

Sir Arhur is very basic. Crane XR700, 4 wire board, Standard Bosch GT40R coil, Echlin ICR13 Ballast. I then fitted a relay to give the 12v boost to the coil for starting purposes, switched by the starter relay.

 

Found what I used when I sorted Sir Arthur back in 1994.

It should help you I hope.

When you unplug that ECU, pay particular attention to the "Green Death" growth that may be in that plug/socket. I use Lemon Juice (from a Lemon not a bottle) to clean it off, and rinse with water CAREFULLY.

D Jetronic 1.pdf

D Jetronic 2.pdf

 

Citric acid. Not bad. Some environmentaly friendly commercial
cleaning products have gone to oranges for it. As FLA and CA
are famopus for oranges and juice, the canners must have lots of
rinds to be used for that.


From time to time, I buy lemon juice in the bottle. I think it is
intended for use in mixing drinks. I use it in the kitchen for cooking.
Lemon and butter sauce !! Olive oil and lemon juice on salad.
Add cold water and sugar for a quick lemonade. A squirt in hot or iced tea! Soda water, sugar and a shot of lemon oughta make a decent
refreshing drink on a hot day.


Add Vodka or tequila, optional.


I've never looked to see if it is "straight" or diluted with water.


Got try a bit as a corrosion cleanser....


Carl

 

Must try a bit, edited....


Carl

 

1. I have the OE ballast resistor in my car.
2. I also have 12V to coil when starting, thru a relay.
3. Injectors have all been professionally cleaned & tested.
4. When I removed the ECU plug it looked very clean, almost like new.

 

Now there were a couple old D-jet cars I did work on with the same problem. One little Beck-Arnley manual I had at work had a good rundown on troubleshooting. For Your problem it said first thing to check was to make sure all connections on the injectors were tight. Those small female connectors are notorious for weakening. Just tighten them up so they have a tight fit to the injectors. I found that alone was the entire issue with an old Volvo, and made a big difference on a couple VW's running that system.

 

Hi, had a very similar issue with my pre he , check for any breakage in the wiring to the coolant sensor. On my wiring diagram its pins 23 and 24 on the ecu you will need to check for continuity. Good luck.

 

What? random as hell