75 with D-Jetronic. Unknown history, and has sat for an
unknown number of years. Oil pressure a bit low but OK'ish and sensor/instrument may be a bit off.
Symptoms: Extremely lumpy running, about like a 4 pot running
on three cylinders. B-bank running fine, A-bank utterly crap.
Lumpy to the point of shuddering on accelleration then
vibrating on further accelleration.

What I have done so far:
1) Replaced plugs, plug cables and dizzy lid.
2) Checked that all injectors are clicking and equally sounding
so.
3) Checked fuel pressure in both banks as per book, spot on.
4) Checked compression, one down outside specs by 10%. Right up
when a little oil poured into the cylinder and retested so
assuming worn cylinder/rings.
5) Checked for spurious air leaks, none found.
6) Checked coolant temp sensor.
7) Pulled the connectors from the cold start injectors.
8 ) Ran a full dosis of Forte internal engine cleaner, poured
into cylinder, left for two days, blew out residue, ran engine
till warm and replaced oil. Initially smoky engine and then
clear exhaust. On starting cold today some 20 secs of smoke
when revving a bit then nothing more.
9) Vacuum gauge steady when T'ed into the vac plumbing to the
pressure sensor, and in acceptable range.

What now?

 

Hello,

Are you actually getting spark on all cylinders on A bank? If you haven't already, pickup a cheap in-line spark tester and if you really want to test, pickup a few of them so you can gauge light intensity.

You may be fighting an OPUS issiue (the ignition amp located in the valley of the motor), or a weak coil. I find these motors to be very sensitive to bad wires and weak coils. I chased a slight idle lump for months, and it was finally a small tear at the end of a wire about the size of your finger nail!

Also, the OPUS modules cook due to heat, as does the associated wires to triggers, really inspect the insulation at the connections. Many guys have relocated that module to the bulkhead above the radiator (Jaguar actually sold a kit for the same), and you can get refurb'd and updated units, but they are not cheap. Lastly, with the cap off, is it dirty (sooty) in there? If so, could be trigger issue on the distributor side.

It sounds electrical (is your tach working??) to me.

Good luck.

Jeff

 

Thanks for the input. The amp is a reOPUS. I have not replaced the coil, but as a starting point I have primarily chased the non-common items as B-bank runs perfectly. It might be down to luck of course despite a dying coil. And rev counter seems to follow revs faithfully without the sudden death usually seen when there are basic ignition troubles. I will have a rerun with the in-line spark tester though.

Next I suppose is to pull all the injectors in A-bank and put them in the bench tester again :-(

 

At this stage I would be checking the trigger board.

If its a 3 wire board, that is the original, and has "reed switches" to fire the injectors. Reliability is not good.

An update board, 4 wire, has hall effect sensors, and reliabilty is NOT an issue, PROVIDING that the 4th wire is actually connected to a 12vIGN source, and not the coil as I have seen many times.

The magnet in the heel of the rotor is different for 3 wire, and 4 wire, and I have NO answer as to why, it just is.

Having typed all that, I doubt that is the root cause of the bank firing issues.

Next would be the sitting time you stated. The injectors may well be "clicking", but I doubt the needles are actually lifting off the seats. Get yourself a small "tack" hammer, as apposed to a BFH, and with the engine running give the injectors a TAP, not a WHACK, just a solid TAP. This has worked for me numerous times on the PreHE and the HE. The injectors are a solid little sucker, so dont be scared, just common sense.

A heavy dose of injector cleaner in minimal fuel in one of the tanks will also do no harm.

Obviously removal and clean is the ultimate, and those injector hoses should be replaced anyway.

 

Thanks it is reOPUS with hall effect trigger. I'll try the tiny tap trick.

 

Come to think of it I took an injector apart a few years ago. So if the stethoscope detects loud clicking the needle is moving. But there is no telling if the injector is (partially) gummed up or residue from sitting there for a while has lodged itself somewhere. Fuel pressure in each rail holds up well though so it does not look like any are stuck open.

 

Run a fuel injection cleaner thru the system. Not just the bottle in tank. Need to use the pressurized flush system. If still a stumble check velocity of injectors on a bench tester.

 

We are on a roll here.

Calls for a fresh JD in my opinion.

The PreHE injectors are more of a squirter than a sprayer. They really shift some fuel compared to the HE and other more modern injectors.

The pressure hold is GOOD.

The PreHE did also suffer from sticky valves after years of sitting. Usually random throughout the engine, not limited to one bank like you got.

One of my PreHE's (in about 1994) did similar, and I simply let it run, with about 10ltrs of fuel, and 3 bottles of injector cleaner (1 bottle treats 60ltrs), and after the BBQ was done it was on 10 cylinders, so we shut it down. Next morning it started on about 7, and went to 12 quickly. Still running today at 500000kms. Never did get around to pulling the injectors. Some serious "tapping" went on, trust me. Sometimes after a few weeks sitting, its a tad hissy, but settles soon enough.

 

Will pull all injectors in A-bank tonight and do full bench test.

 

Injectors all ovef the place. Will try anothef bout of cleaner.

 

On the rare occasions I clean injectors when I have them out for some other reason, I attach about 12" of hose to one injector at a time, supprt that hose vertically, and fil it with Paint Thinners.

Apply some compressed air, about 10psi or so to that hose.

2 people works well here.

SAFELY plug 2 wires into the injector, and with the other ends a LONG WAY from where you have the thinners, activate the injectors, by a simple "flash" method, DO NOT hold the votage, the injectors will burn up.

I use a part flat car battery, or similar, as it does not take much to trigger them.

Once the gunk is gone, follow with some petrol to remove the thinners.

This has worked for me for a very long time. I have never had injectors "professionally cleaned".