Fuel Mixture Problems - Car won't start when mixture set properly

[Michael]

Yes the mixture is set in closed loop. I think you have one or more problems and adjusting mixture is just a band aid fix. Mixture is the absolute last thing to set...after ALL other issues are resolved.

The thing is that a PRV running CIS can run well with a LOT of things out of whack. Vacuum leak, just adjust the mixture to compensate. Bad PPR Orings? Adjust the mixture. By the time that the ol standby fix of screwing with the mixture doesn't solve the problem, you got so much wrong that you don't know where to begin.

[spikeygg]

Yes the mixture is set in closed loop. I think you have one or more problems and adjusting mixture is just a band aid fix. Mixture is the absolute last thing to set...after ALL other issues are resolved.

Yeah, I get it. That's not the first time I've heard this argument. However, I CANNOT get the car started and running without adjusting the mixture richer... unless you have a solution to make that happen without adjusting the mixture?

By the way, I have a CO monitor in the garage and this is what it looked like with the car running yesterday morning.
CO while DeLorean idles.jpg
You can see the back side come down about half-way, that was after I leaned out the mixture, got the car idling more favorably and the O₂ signal finally cycling.

The blips later in the day were me trying to start it again (without any further mixture adjustments). It's a BIG garage with all exterior man doors (2), windows (2) and garage car doors (3) open.

Based on this chart from motor.com article: DIAGNOSING A LEAN-RUNNING ENGINE CO gets worse as the engine runs richer:
lean1_0118.jpg

With it able to start, it's clearly too rich but with it tuned properly for hot operation it cannot be started.

I have the fuel pressure tester coming so I'll try that out and see if I can determine that the WUR is broken.

@Michael do you have modified cams in your car?

[Michael]

Yeah, I get it. That's not the first time I've heard this argument. However, I CANNOT get the car started and running without adjusting the mixture richer... unless you have a solution to make that happen without adjusting the mixture?

By the way, I have a CO monitor in the garage and this is what it looked like with the car running yesterday morning.
CO while DeLorean idles.jpg
You can see the back side come down about half-way, that was after I leaned out the mixture, got the car idling more favorably and the O₂ signal finally cycling.

The blips later in the day were me trying to start it again (without any further mixture adjustments). It's a BIG garage with all exterior man doors (2), windows (2) and garage car doors (3) open.

Based on this chart from motor.com article: DIAGNOSING A LEAN-RUNNING ENGINE CO gets worse as the engine runs richer:
lean1_0118.jpg

With it able to start, it's clearly too rich but with it tuned properly for hot operation it cannot be started.

I have the fuel pressure tester coming so I'll try that out and see if I can determine that the WUR is broken.

@Michael do you have modified cams in your car?

Mine has cams. My car was acting very similar to yours. It progressively got harder and harder to start cold(would fire up but stall out almost immediately). I usually only had to restart it 2 or 3 times but then I was having to restart 7-8 times.

I too suspected the WUR and ordered one but I read on Dgo's site that they recommended a new FD and injectors at the same time. Not sure why injectors as they are either working or they are not and easy to test but since I did new injectors the previous year anyway, I just got the WUR and FD.

Replaced the WUR first since it was easiest and that was my hunch. It didn't help. The FD corrected my issue. After replacement, I had to lean my mixture out almost a full turn!

[spikeygg]

Mine has cams. My car was acting very similar to yours. It progressively got harder and harder to start cold(would fire up but stall out almost immediately). I usually only had to restart it 2 or 3 times but then I was having to restart 7-8 times.

I too suspected the WUR and ordered one but I read on Dgo's site that they recommended a new FD and injectors at the same time. Not sure why injectors as they are either working or they are not and easy to test but since I did new injectors the previous year anyway, I just got the WUR and FD.

Replaced the WUR first since it was easiest and that was my hunch. It didn't help. The FD corrected my issue. After replacement, I had to lean my mixture out almost a full turn!

OMG, $700 for an FD rebuild +core! Is that how much you paid? I'm guessing Dgo you referred to is https://www.deloreango.com/? Why not buy from the official https://store.delorean.com if the price is so close?

Also, is there any way to test the Fuel Distributor? I'd hate to throw $700 at it and find out it was not the problem. :-/

[Michael]

OMG, $700 for an FD rebuild +core! Is that how much you paid? I'm guessing Dgo you referred to is https://www.deloreango.com/? Why not buy from the official https://store.delorean.com if the price is so close?

Also, is there any way to test the Fuel Distributor? I'd hate to throw $700 at it and find out it was not the problem. :-/

Personally, I don't consider DMCH to be a benchmark of quality parts. I believe all the vendors make substandard parts in some areas(with DeLorean Industries being the possible exception). When I did mine, the FD was $640.00 when I bought it. The deciding factor in my case was with Dgo, my cores were to be returned after purchase and my core charge refunded. If I recall they even sent a call tag for shipping, not to mention Dgo offers free shipping. With DMCH I would pay shipping BOTH ways.

With DMCH, your old parts are sent to them to rebuild and sent back and I didn't like the idea of my car being apart and at their mercy for turn around time. Also DMCH was pretty clear that not all WURs were able to be rebuilt so I didn't want to again, be at their mercy.

I checked all I could with my limited knowledge. I had zeroed in on the WUR but turns out in my case the FD was the culprit(or maybe both?). I was willing to throw some money at it and hope for the best which thankfully worked.

That does remind me to ask if you removed the FD and checked the plunger operation? It should be butter smooth and not stick or grab in the least. Also check the primary pressure regulator for damaged or worn o rings. There is a kit that includes the 2 rubber rings and a new seal for a few bucks. May be worth a try because the orings can look good on the plunger but be hard and deformed. As cheap as they are it's not a bad idea to replace them every few years.

[spikeygg]

That does remind me to ask if you removed the FD and checked the plunger operation? It should be butter smooth and not stick or grab in the least. Also check the primary pressure regulator for damaged or worn o rings. There is a kit that includes the 2 rubber rings and a new seal for a few bucks. May be worth a try because the orings can look good on the plunger but be hard and deformed. As cheap as they are it's not a bad idea to replace them every few years.

I have never pulled my fuel distributor off before. Is it easy to do for checking the plunger operation? Can I do it leaving all the fuel passages intact?

I just watched this video that explains the fuel distributor and injection flap, his plunger seems to move on its own! I think I see the o-ring on the bottom of the FD, looks like maybe a couple of inches in diameter. I'll have to poke around and see if I can find some example images or video of the primary pressure regulator o-rings because I'm not familiar with where those are... I don't suppose you have any pictures to share for that?

Thanks for the info -- having things to check is always good.

[Michael]

I have never pulled my fuel distributor off before. Is it easy to do for checking the plunger operation? Can I do it leaving all the fuel passages intact?

I just watched this video that explains the fuel distributor and injection flap, his plunger seems to move on its own! I think I see the o-ring on the bottom of the FD, looks like maybe a couple of inches in diameter. I'll have to poke around and see if I can find some example images or video of the primary pressure regulator o-rings because I'm not familiar with where those are... I don't suppose you have any pictures to share for that?

Thanks for the info -- having things to check is always good.

Yes you can lift the FD off the metering assembly with all lines attached. The plunger is just a friction fit and it will fall out so be careful.

The primary pressure regulator is on the side. If memory serves, it's a 15mm and will come out as it's under sprung tension so make sure you remove the last few threads slowly and carefully. Also have a telescoping magnet handy to aid in getting all of the assembly out.

[Helirich]

On that PPV, when you remove the threaded end with the spring, don't walk away with those parts if the little cup stays in there. Some times residue pressure will pop it out after a few seconds/minutes. I recommend putting a rag to catch it or get it out immediately. If it pops out while you're not looking and falls down in the mess of tubes and hoses, you won't be happy.

Also, Michael is right about checking the FD plunger. Mine was stuck. I can't remember the exact symptoms, but ran poorly. I just pulled the FD with all lines attached and got the plunger loose by twisting it. That was the beginning of my car running good.

[spikeygg]

Okay, I'm out here looking at it and it definitely looks like I need to break into the fuel lines to take the FD off the intake. Two of the screws are accessible but one is under a banjo bolt...

PXL_20210829_160447750.jpg

[Michael]

FWIW I just now watched the Dwell meter vid. You got no action going on there at all. When is the last time you changed the O2 sensor? Does the idle circuit work properly? That is something to address in the near future.

You may have to break that bolt and move the line to access the third screw. You should replace the seals once you break them loose but for testing purposes, just retighten and make sure they don't leak after you check the plunger.

I don't know why they used standard screws on the FD. If they are hard to break loose, don't force it. Put a little PB blaster on it and if that doesn't work use an impact driver(the hand tool if you have it but hit it lightly because the FD can crack).