Club 80-90 Forums

Hi all,

Over the last 2 years I built myself a 'new' DJ engine; apart from the casing and some add-on parts, everything is new: crankshaft and camshaft, pistons, cylinders, tappets, bearings, etc. Last week I replaced the old DJ engine in my van with this new one, taking all the fuel supply from the old engine and leaving the electronics intact/connected as much as possible.
The day before yesterday was the big day: I double checked everything, made the basic settings for valves and ignition, said a quick prayer and started the engine. A small miracle: it ran like a dream. No ticking valves, no weird noises, no trembling - I was in seventh heaven. Then I ran it for a quarter of an hour at ± 2000rpm, turned back the idle screw quite a bit to have the engine idling; I was pleased to see how quiet it ran and then turned it off.
Yesterday, the engine started immediately at the first turn of the key and then ran as smoothly as the day before. I checked the ignition timing with an ignition timing gun, but that was (coincidentally) exactly right. So off I went for a test drive. This went well at first, but after a few kilometres of (smooth) driving, the engine seemed to run on only 3 (2?) cylinders. The spirit was completely gone, acceleration was difficult and top speed was about 50kmh.
So back to the garage to see if I could find the cause. All four cylinders seemed to get spark and fuel, but the spark plug of cylinder 3 was quite blackened and those of cylinders 1 & 2 slightly blackened. Unfortunately, the engine would now only start for a short time and shut down again after 1, 2 or sometimes even 5 seconds.
Other noticeable things since the rebuild: the LPG system (which I wasn't to use for the next 1000 km anyway) and the electric windows don't work anymore (no power).
Does anyone have any idea what the problem could be?

Aside from the leccy windows now not working...surely not connected with engine issue...please tell the forum whether your DJ is running carb or Digijet?

Actually re-reading l suspect Digijet. Two years for all the anxcillaries to sit about doing nothing is going to make it difficult to suggest where to start...
ECU faulty
Bad fuel blocking fuel injectors. Check spray pattern with new fuel.
What timing position are you using?
Temp 2 sensor.
The list is very long

Hi Maxstu,

Thanks for the replies. Indeed: DigiJet.
All ancillaries, including ECU, came from the previous engine and were working fine up until I started the swap 2 weeks ago.
Fresh fuel was taken in right before the swap.
Timing position, as mentioned, is on the required position.
Temp2 sensor is good guess though, will have a look into it.

Bentley has a test for temp 2 sensor. If needed let me know.
Also, with respect, what timing are you running? Did you disconnect vacuum and single yellow connector under coil. Then plug together two connectors from box on the wall next to ignition amplifier (another culprit)?
Clean out from both side with carb cleaner and check resistance of the ICV. It is buzzing, right?

Thanks again.
For the timing setting: it's spot on the mark on the pulley @ 10º before TDC. Of course I disconnected the vacuum and the single yellow connector and plugged together the two connectors from the DLS. And the ICV is buzzing.
The Temp2 sensor is new, the wiring is a bit dodgy though. That's my first target.

Okay. Keep updating. Here to help.

Temp 2 unlikely, as that would just enrich and pick up idle revs, not cause a misfire or cut-out. Are you sure it's digijet, not digifant? Symptoms sound just like digifant when it increases fuelling until it floods, caused by a faulty loom, backfeeding through earth shielding on wire to lambda probe. But if it's digijet it can't be that. Perhaps think what might cause similar overfuelling in a d'jet. Air flow meter flap stuck open after a backfire? I'm thinking out loud of unlikely options, as you've already done all the right things.

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As Andrew says could be a wiring fault with something shorting.
Put a carb on it

ajsimmo wrote: ↑28 Mar 2022, 08:21 Temp 2 unlikely, as that would just enrich and pick up idle revs, not cause a misfire or cut-out. Are you sure it's digijet, not digifant? Symptoms sound just like digifant when it increases fuelling until it floods, caused by a faulty loom, backfeeding through earth shielding on wire to lambda probe. But if it's digijet it can't be that. Perhaps think what might cause similar overfuelling in a d'jet. Air flow meter flap stuck open after a backfire? I'm thinking out loud of unlikely options, as you've already done all the right things.

Yes, it's a DigiJet. And the symptoms are quite as you describe, why can't that happen with a DigiJet?
 

So, this morning I took a closer look at the wiring of the Temp2 sensor. It wasn't even dodgy, it was completely loose. I fixed it with a brand new JPT-connector and the engine came to life pretty soon. But I was running irregularly and shaky, like it was on 3 cilinders. When I tried to run it at ±2000rpm, the rpm's went up and down even though I kept the throttle lever in the same position. And then after 6 or 7 minutes it cut out and didn't want to start again. Then the battery started to run down and I was running out of time, so I didn't investigate any further.
Tomorrow I'll be swapping the (new) Temp2 sensor for one I know was working recently, and I'm gone check the valve/tappet setting.

Mass airflow sensor fault perhaps?

luxbus wrote: the symptoms are quite as you describe, why can't that happen with a DigiJet?
 

Because there's no lambda probe, and digijet is an open loop system with no adaptive features. Therefore it can't incrementally alter the fuelling due to feedback, it's a fixed map. Yours must be a "hard" fault.

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Unless of course its a tight exhuast guide grabbing a valve as it warms up. I have warned about this product blemnwith AMC/KS heads numerous times.
It can result in either a misfire or a bent pushrod.

Well, the increasingly bad running of the engine turned out to have a rather silly cause: my own inaccuracy. After having set the basic valve preload during assembly, I failed to tighten the locking nuts on the tappet adjuster screws of cylinders 3 & 4... Now the engine's running fine again.
Thank you all for your input.