General engine/K-jet issues

[PeterBiggerstaff]

Hi Everyone,

Over the past few months, I managed to get 10985 running again, however after a few starts she developed a vacuum leak. I traced this down to my home made aux air bypass seal which was made out of heater hose and gasket sealer.

The seal had melted due to a previous issue with oil that had become severely contaminated with fuel. I found DMC Europe had the correct o-ring and keeper, so have fitted those.

Now though, I'm having issues getting her to run right. She's hard to start, and when she does fire up, she idles at about 700rpm for a few seconds, then speeds up to around 1,700rpm and sits there.

If you pull on the throttle spool, she backfires (in the intake) and the revs drop rather than go up. The more throttle you give her, the rougher she runs until she finally stalls. I've played around with the mix, and while this has made it marginally better, she's still iding too high and still won't rev properly.

I put a video together of the symptoms, its a little hard to hear as the fans run all the time the ignition is on (I'm getting a new relay kit to fix this) but you can hear her backfiring and generally not revving the way she should.

I'm going to get a dwell meter and timing light, but does anyone else have any other ideas? It feels to me like there is still a vacuum leak somewhere, but I'm not very experienced with the K-Jet so not 100% sure.

When she's cooled down, I'm also going to check the vacuum advance, make sure the hoses are firmly attached.


https://www.youtube.com/watch?v=JmL2SmP4vQA

[sdg3205]

Hi Everyone,

Over the past few months, I managed to get 10985 running again, however after a few starts she developed a vacuum leak. I traced this down to my home made aux air bypass seal which was made out of heater hose and gasket sealer.

The seal had melted due to a previous issue with oil that had become severely contaminated with fuel. I found DMC Europe had the correct o-ring and keeper, so have fitted those.

Now though, I'm having issues getting her to run right. She's hard to start, and when she does fire up, she idles at about 700rpm for a few seconds, then speeds up to around 1,700rpm and sits there.

If you pull on the throttle spool, she backfires (in the intake) and the revs drop rather than go up. The more throttle you give her, the rougher she runs until she finally stalls. I've played around with the mix, and while this has made it marginally better, she's still iding too high and still won't rev properly.

I put a video together of the symptoms, its a little hard to hear as the fans run all the time the ignition is on (I'm getting a new relay kit to fix this) but you can hear her backfiring and generally not revving the way she should.

I'm going to get a dwell meter and timing light, but does anyone else have any other ideas? It feels to me like there is still a vacuum leak somewhere, but I'm not very experienced with the K-Jet so not 100% sure.

When she's cooled down, I'm also going to check the vacuum advance, make sure the hoses are firmly attached.


https://www.youtube.com/watch?v=JmL2SmP4vQA

If you played with the mixture WITHOUT a dwell meter you weren't going to do any good. You need to pull your injectors, throw them in clear bottle, re-establish baseline and go from there.

Is your ISM operating correctly? You can visually check this with it removed - have some one turn the key to the second position and see if the ISM valve sweeps. Does it make humming noise?

Ensure the lambda system is getting power. Check you have the correct relay.

Double check your spark plug leads. they're easy to mix up.

Triple check for vacuum leaks, especially around the POA.

Yes, checking timing can't hurt.

[Bitsyncmaster]

Pull the vacuum hose off the ignition distributor and see if that helps. Normally you don't get any advance at idle so that may fix the 1700 RPM at idle. You backfire is probably your timing is set to far advanced.

[David T]

A common problem area is the quadrant link, that piece of the throttle linkage that connects the throttle spool to the throttle arm. The ends wear and develop a lot of play so when you release the gas pedal the throttle arm does not return all the way to it's stop, staying slightly open and not turning on the idle motor. You cannot adjust the mixture properly without some kind of meter. A tiny amount of movement makes a big difference so it must get set properly.

[PeterBiggerstaff]

Thanks again for the ideas guys, I'll have a look into these today.

[PeterBiggerstaff]

Just an update on this....

I suspected one of the spark plugs was cross-threading. When I got the car, this plug had shattered and I had to take all the parts out with needle nose pliers. I layed across the engine bay with my inspection light and I was right, the plug was barley in, despite feeling snug in the thread. I fixed this up and I also swapped the electrical connector on the vacuum solenoid around in case I had this plugged in the wrong way.

I wasn't expecting these steps to solve anything, but it was raining and I haven't got a timing light or automotive multi meter yet to fix up the dwell and timing. I gave her a go anyway and she started right up this time, and I was suprised to find she sped up to about 1.5k for about 20 seconds, then dropped down to 800ish... still a tad high but much better!

I still can't rev her though, applying throttle just makes her idle rougher until she stalls, but she's not backfiring any more.

I am going to get a multimeter and timing light this week, I'm also going to pull the injectors as per several people's recommendations. I have 2 questions around this, do you pull them all at once, or do you test one at a time? Also, how do you remove them, they feel very fragile to me and I'm scared of breaking something.

[sdg3205]

Just an update on this....

I suspected one of the spark plugs was cross-threading. When I got the car, this plug had shattered and I had to take all the parts out with needle nose pliers. I layed across the engine bay with my inspection light and I was right, the plug was barley in, despite feeling snug in the thread. I fixed this up and I also swapped the electrical connector on the vacuum solenoid around in case I had this plugged in the wrong way.

I wasn't expecting these steps to solve anything, but it was raining and I haven't got a timing light or automotive multi meter yet to fix up the dwell and timing. I gave her a go anyway and she started right up this time, and I was suprised to find she sped up to about 1.5k for about 20 seconds, then dropped down to 800ish... still a tad high but much better!

I still can't rev her though, applying throttle just makes her idle rougher until she stalls, but she's not backfiring any more.

I am going to get a multimeter and timing light this week, I'm also going to pull the injectors as per several people's recommendations. I have 2 questions around this, do you pull them all at once, or do you test one at a time? Also, how do you remove them, they feel very fragile to me and I'm scared of breaking something.

You're off to a good start.

You wont break the injectors, perhaps the factory lines if you still have them, but its unlikely.

all 6 injectors go into their own bottle. Label the bottles with the cylinder numbers (as seen on the valve cover). Jump the RPM relay to run the fuel pump, back off the mixture screw until the injectors stop firing, and are just on the threshold. If they aren't firing, richen the mixture until they start to fire then back it off to threshold again. That's more or less your baseline from which to start tweaking your mixture. There are lots of threads about adjusting the mixture, videos too.

Have you verified your spark leads are all correct, having traced them from the distributor to each plug? If you have one backwards it will seem to idle okay, but may vibrate more and will not accelerate easily.

[Bitsyncmaster]

Pulling the injectors to base line set the mixture is mostly for an engine that will not start. You do get to see if there is a bad injector not spaying correctly but you should be able to set the mixture correctly with a dwell meter if your lambda system is functional.

[sdg3205]

Pulling the injectors to base line set the mixture is mostly for an engine that will not start. You do get to see if there is a bad injector not spaying correctly but you should be able to set the mixture correctly with a dwell meter if your lambda system is functional.

Dave is right. I wrote that late at night half asleep. I failed to mention that you're looking for volume output of the injectors. Manual has spec. They should all be in the same ballpark. If you've been fiddling with the mixture blindly it will be easier to set it from baseline.

[David T]

Dave is right. I wrote that late at night half asleep. I failed to mention that you're looking for volume output of the injectors. Manual has spec. They should all be in the same ballpark. If you've been fiddling with the mixture blindly it will be easier to set it from baseline.

Since you found that plug messed up you should pull all of them. Do a compression test and then replace and regap new plugs. As important as equal volume is out of each injector, they must all spray a good pattern and open at the same pressure. Best to send them out for testing and cleaning. Probably need new injector seals too.

[PeterBiggerstaff]

Thanks again for the help, I'll get on to this next weekend. Also, someone mentioned the idle motor....

I have a feeling it's not working, Again, I'll verify this weekend but previously I have found it either runs at 100% all the time, or not at all. I am in the process of ordering a new relay kit from DMC, so this may fix that.

[DMC5180]

The relay kit will do nothing for the Idle Speed Motor.




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[sdg3205]

Thanks again for the help, I'll get on to this next weekend. Also, someone mentioned the idle motor....

I have a feeling it's not working, Again, I'll verify this weekend but previously I have found it either runs at 100% all the time, or not at all. I am in the process of ordering a new relay kit from DMC, so this may fix that.

You can test the IsM as I mentioned above. If you want a quick and dirty test, unplug the black harness from it at idle. If you stall or if the idle gets worse, it's working.

[Horsebox]

You could check that your throttle spool is tripping the the little micro switch when your foot is off the accelerator pedal. If your hands are small enough you can just about get behind the switch to pull the harness off and attach DVM leads to the two terminals to make sure the switch closes electrically. This switch is vital for your Idlespeed.

What you describe with your idle sounds like the ISM is electrically powered but isn't getting the signal from the microswitch to actually control your idle. So it just goes to its default setting of about half open and hence your high idle.

[Horsebox]

I just watched your video again and noticed that there's no plug to fill the hole where you put your 3mm Allen key in to adjust the mixture. I know it's only a little hole but that's a big vacuum leak...about 2% CO. Next time you have the engine running stick your thumb over the hole and see if the running gets better.

Trying to diagnose a fuel system that is based on pressures without Kjet pressure testing kit is like trying to diagnose an electrical problem without a voltmeter. I.e a waste of time.

Have fun, it will be something simple in the end!

[opethmike]

Is it just me, or is that long bolt that joins the throttle body and the w-pipe missing in the video?

[DMC5180]

Is it just me, or is that long bolt that joins the throttle body and the w-pipe missing in the video?

It's not just you, it's missing. Nice observation.


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[opethmike]

Yes, yes it is; so you're going to have a gnarly vacuum leak between the w-pipe and throttle body. If that bolt is missing, I'd also check that the big o-rings and plastic rings are in place.

[DMCMW Dave]

That's a fun one to find locally - it's a long 7MM bolt. Not exactly a hardware store part. M7 x 75. DMC Part 102286

[PeterBiggerstaff]

Hey good spotting guys, on the missing bolt... See this is the issue with a car that a previous owner has hacked about so much, I never knew there was supposed to be a bolt in there!

The O-rings are there, as I got these with the manifold gasket set. I'll get a bolt and the grommet to fill the mix hole. I have checked the throttle spool and the microswitch, these are both set correctly.

I still need to test the idle speed motor, which I'll do this weekend (get my wife to turn the ignition on while I listen to the motor. I've got a ton of things to try/test/fix up now, so thanks for everyone's input.

[PeterBiggerstaff]

That's a fun one to find locally - it's a long 7MM bolt. Not exactly a hardware store part. M7 x 75. DMC Part 102286

I don't buy anything locally, people here have a habit of making things too hard and wasting my time, I buy almost everything (even nuts and bolts) from DMC. It costs more but saves hours of running around and chasing people here in NZ.

[DMCMW Dave]

The two rubber o-rings are not anything weird but they must have a backer ring (OEM is teflon) behind it. If you don't have the backers, doubling the o-rings will usually work ok.

[sdg3205]

The two rubber o-rings are not anything weird but they must have a backer ring (OEM is teflon) behind it. If you don't have the backers, doubling the o-rings will usually work ok.

This Dave (Dave S) is the gentlemen who can elaborate on testing the ISM if/when you need to.