From the block to the throttle body to the coolant pipe.
Coolant pipe feeds water pump.
Warm/hot water helps vaporize gasoline when it’s cold.
Coolant pipe feeds water pump.
Warm/hot water helps vaporize gasoline when it’s cold.
D-jet trouble shooting
- Thread starter Drew20
- Start date
Cool, ta for confirming
Having a seized bolt adventure, guessing none of this has been apart since late 80s
Having a seized bolt adventure, guessing none of this has been apart since late 80s
“Adventure”
Lol...
Lol...
So, an update.... the outside of the engine is pretty filthy, it's obviously been cleaned, and the bits that can be seen in the engine bay look ok, but as soon as I dug underneath anything there was years of crud, and a lot of the bolts on the cooling system were seized solid, not been touched in a long while, so I've snapped four in all, but I have spares.
The contrast with the inside of the engine is stark, as the inside of the cooling system is mint, someone has been loving this engine. Which leaves a question for me, as there was no blockage on the small circuit I thought could be blocked, not even a hint of a blockage. I've blown it all through with compressed air to be sure.
The temp readings I took from the pipes clearly indicated no flow, or very restricted flow, through this circuit, so I'm a bit baffled. An air lock maybe??
To get the throttle body off, the valve cover comes off. First time I've seen inside the engine, totally mint. Pleased to see rockers glinting in the sunlight!!
Will be testing the components, new stat, new gaskets, clean and rebuild.
Going to fix an oil leak on the upper timing cover also
The contrast with the inside of the engine is stark, as the inside of the cooling system is mint, someone has been loving this engine. Which leaves a question for me, as there was no blockage on the small circuit I thought could be blocked, not even a hint of a blockage. I've blown it all through with compressed air to be sure.
The temp readings I took from the pipes clearly indicated no flow, or very restricted flow, through this circuit, so I'm a bit baffled. An air lock maybe??
To get the throttle body off, the valve cover comes off. First time I've seen inside the engine, totally mint. Pleased to see rockers glinting in the sunlight!!
Will be testing the components, new stat, new gaskets, clean and rebuild.
Going to fix an oil leak on the upper timing cover also
It’s likely the small water fittings are blocked on the block at back by cylinder 6 or on coolant tube.
Look directly below intake for cylinder 6.
Often plugged.
Look directly below intake for cylinder 6.
Often plugged.
That's what I thought might be an issue, very difficult to access the port which feeds the TB and the sensor "manifold", no clear line of sight. But I blew (and sucked - carefully) on the attached coolant pipe and it is clear. Ive blasted it with compressed air to be 100% and coolant shot out the pump intake!
I'm pretty sure it was not previously blocked. I've not managed to get the hose of that port though, difficult access
Anything else I can do to be 110%? Keen not to have to take this all apart again, if the issue is still there after the assembly
Thanks again Don, good to have a wingman on this job as this M30 has different plumbing to my previous E24
I'm pretty sure it was not previously blocked. I've not managed to get the hose of that port though, difficult access
Anything else I can do to be 110%? Keen not to have to take this all apart again, if the issue is still there after the assembly
Thanks again Don, good to have a wingman on this job as this M30 has different plumbing to my previous E24
An update on this. I stripped the small coolant line through the TB and the small sensor/ AAV manifold, tested the various components and reassembled. All of the various bits worked fine, coolant temp sensor was in spec, AAV closes ok, I think. Actually when should the AAV close? I boiled it up and it started closing noticeably at 70C and was fully closed at 80C. This was testing by me blowing through the pipe whilst I boiled it up.
On reassembly I carefully bled the line, to ensure no air-lock, and it's now fine with temp of 80C at various points on the circuit. Not sure if there was a blockage or if it was airlocked?
I also took the stat out and tested that. The stat started opening at 80C and was wide open at 90C. This looks to be for an auto car, I read that on a manual the stat should start to open at 84C. Reassembled with studs instead of bolts, which might offend the purists but should make it a lot easier to undo them in the future!!
I also reset the ignition timing, think it was a bit retarded previously, now set to 22 degs at 1800rpm
Seems to be running better on partial and full load (might be just in my head?) but the idle is still poor.
Have built a t-piece with a valve so I can isolate the MAP from the manifold and apply extra vac, as per Don's suggestion.
On reassembly I carefully bled the line, to ensure no air-lock, and it's now fine with temp of 80C at various points on the circuit. Not sure if there was a blockage or if it was airlocked?
I also took the stat out and tested that. The stat started opening at 80C and was wide open at 90C. This looks to be for an auto car, I read that on a manual the stat should start to open at 84C. Reassembled with studs instead of bolts, which might offend the purists but should make it a lot easier to undo them in the future!!
I also reset the ignition timing, think it was a bit retarded previously, now set to 22 degs at 1800rpm
Seems to be running better on partial and full load (might be just in my head?) but the idle is still poor.
Have built a t-piece with a valve so I can isolate the MAP from the manifold and apply extra vac, as per Don's suggestion.
An update to my update
Checked the d-jet coolant temp sender with the engine up to temp, and it was down to 280 ohms, which correlates to ~90C. Before this mini project sender was reading about 530 ohms, which is about 60C. So I'm not sure what I did, but I do now have coolant flowing in that small circuit, maybe it was blocked, maybe air-locked? Phew!
Also checked the CO at idle, and it is down at 1.7-2.1 (fluctuating), with an idle of 900-1050 (again fluctuating). Manifold vac was 15". If I isolated the MAP and upped the vac a bit with my vac pump (as per Don's suggestion) the engine stalled straight away. Not sure what this means, I was only upping the vac to 16", so well within expectations for manifold vac at idle. I saw on the link below idle vac should be 14-18" (that's on a MB d-jet set up)
https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm
Anyway, think I'm good for now, I will still do a check for false air leaks. I don't have an o-ring on the dipstick, so some more to sort
Question: assuming I'm now running much closer to stoichiometric mix, will the carbon build up on pistons and head start to go away itself, or do I need to take action to clean it up? Seafoam or similar?
Checked the d-jet coolant temp sender with the engine up to temp, and it was down to 280 ohms, which correlates to ~90C. Before this mini project sender was reading about 530 ohms, which is about 60C. So I'm not sure what I did, but I do now have coolant flowing in that small circuit, maybe it was blocked, maybe air-locked? Phew!
Also checked the CO at idle, and it is down at 1.7-2.1 (fluctuating), with an idle of 900-1050 (again fluctuating). Manifold vac was 15". If I isolated the MAP and upped the vac a bit with my vac pump (as per Don's suggestion) the engine stalled straight away. Not sure what this means, I was only upping the vac to 16", so well within expectations for manifold vac at idle. I saw on the link below idle vac should be 14-18" (that's on a MB d-jet set up)
https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm
Anyway, think I'm good for now, I will still do a check for false air leaks. I don't have an o-ring on the dipstick, so some more to sort
Question: assuming I'm now running much closer to stoichiometric mix, will the carbon build up on pistons and head start to go away itself, or do I need to take action to clean it up? Seafoam or similar?
Based solely on your description, it is hard to measure "carbon buildup." It is therefore difficult to respond with any degree of certainty. That said, some light fluffy deposits will typically be removed from the combustion chamber with some hard driving. Consider that so-called "top tier" fuel retailers sell fuel that contains additives that reputedly remove carbon via normal engine operation, e.g., Chevron's "Techron" nee "Techroline." This may be a safer approach than dumping seafoam or similar down the intake manifold. But if excess carbon is keeping you from getting a good night's rest, there are plenty of options, including water/steam.
https://www.hemmings.com/magazine/mus/2008/01/The-Lost-Art-of-Chemical-Carbon-Removal/1567737.html
https://www.dslreports.com/forum/r27273901-Decarbonising-Engine-with-Water
Time for an Italian tuneup....
That sounds like the fun bit, will see how we get on then, re-check plugs in a few hundred miles
I've heard of water decarb, sounds easy enough
Ta
I've heard of water decarb, sounds easy enough
Ta
Rex Kapriellian
Well-Known Member
What’s an Italian tune up? : - )
Rex Kapriellian
Well-Known Member
Any updates to this thread?
Taking Your Car To Redline Can Remove Harmful Carbon Deposits
Does the Italian tune-up actually work? It depends.
Rex Kapriellian
Well-Known Member
You inspired meTaking Your Car To Redline Can Remove Harmful Carbon Deposits
Does the Italian tune-up actually work? It depends.www.roadandtrack.com
Well I tried a number of things, and the one that made the difference was an adjustment to the waxstat in the warm up slide valve thing. This was passing air, very slightly, when the car was warm. Once this was tweaked the mixture was much much better. Idle CO levels are still a bit higher than spec, but pretty good
TBH I can't figure this all out, as a slight vac leak at the slide valve should be offset by the idle screw settings. D-jet surely has no such thing as unmetered air....?
#Mysteries of d-jet
Rex Kapriellian
Well-Known Member
Hmmm. I replaced mime with an SF Don “the Don” rebuild slide valve. My idle is ok. Just don’t have another coupe to measure up the performance to. I just know I’m running a little under powered. a friend mentioned maybe time to change the fuel filter or possibly a pinched fuel line. I’m going with all the low hanging fruit first.
Rex Kapriellian
Well-Known Member
A car sitting outside for a longtime is undergoing a S U N test.
www.jetronic.org (used to be "dr. d-jet") is indispensable for us d-jet users...