Hot start problem

[aludden]

Well, now that I finally got my car running again, I would like to use it!

But I can't go anywhere unless I leave the engine running, because it won't start when hot. I already had posted about this months ago, but still have not been able to resolve it.

I have changed the fuel accumulator, fuel filter, viton in distributor, had Hervey clean and check the injectors, put new spark plugs, wires rotor and cap, and changed the engine vacuum hoses, as well as the mode switch diaphragm. I don't see any vacuum leaks. I re-checked the viton.

I ordered a fuel pump check valve but Hervey tells me those never go bad (I have one of his fuel pumps).
What he suggested is that maybe I'm running too lean. He said to get a 3mm allen wrench and put it where the little plug is in front of the accumulator and give it a 1/4 turn clockwise. I tried different allen wrenches I have, but nothing seems to bite. When I put the allen wrench in the hole it pushes the air intake plate down and I can see it touches a brass fitting. Is that what I am supposed to turn? Here's a picture:
8465

Another thing that is happening is that the accelerator cable seems to be sticking. I have a fast idle sometimes 1500-2000 RPM, and I can get it back down to 900-1000 by pushing on the little arm by the microswitch (see arrow below). I see there is a spring there - maybe it's bad? Or something else is causing it to stick?
8466

Even when I make sure to push it first and then turn off the engine, I still have the hot start problem. If I try to restart after a couple of minutes, it runs really rough for a few moments. If I wait more than five minutes, it won't start.

Other than that, it starts cold right away, and runs beautifully!

Thanks!
Alex

[jawn101]

Search the forum for CO Adjustment and you'll find plenty of threads. And all of them will tell you not to muck about with that setting unless you're absolutely, positively sure you need to.

Hot start issues could be many, many things.... If you already did your accumulator though that's the most common one I can recall off the top of my head.

[DMC3165]

Have you checked the o-ring inside the Primary pressure regulator? This is another notorious problem area with hot start problems. Also is a good place to look being that you already changed the accumulator. Just an FYI If you haven't checked it, The O-ring can be a little stubborn to get out. If it dosen't come out with the PPR after you've removed it, try cranking the engine for a split second and allow fuel to force out the o-ring from inside.

[Bitsyncmaster]

Just pull the air cleaner off so you can test if your problem is due to rest pressure time.

Start the engine, then shut it off. Go lightly press on the air plate and feel it has pressure. Don't press it down, just test for pressure. Keep doing this at intervels (15 min) until it moves easily. Your looking for 4 hours of holding rest pressure so you don't have any warm start issues.

Your problem may not be related to rest pressure.

[Spittybug]

Another thing that is happening is that the accelerator cable seems to be sticking. I have a fast idle sometimes 1500-2000 RPM, and I can get it back down to 900-1000 by pushing on the little arm by the microswitch (see arrow below). I see there is a spring there - maybe it's bad? Or something else is causing it to stick?

Try turning the screw in your photograph and let the linkage move back a bit more to engage the microswitch. Of course, if the standoff screw is already backed off and is not the obstruction to hitting the switch, you may indeed need to lube up your throttle cable and or replace that throttle return spring.

PLEASE don't go playing with the mixture setting until all other things are ruled out. To say that it is a slippery slide would be an understatement.

[tgraham]

I have changed the fuel accumulator, fuel filter, viton in distributor

Are you absolutely sure that there's not a fuel leak around any of these fittings?



What he suggested is that maybe I'm running too lean. He said to get a 3mm allen wrench and put it where the little plug is in front of the accumulator and give it a 1/4 turn clockwise.

I think this is taking you down an entirely wrong path! Adjusting the quantity of fuel flowing to the injectors will have no bearing on whether the system maintains rest pressure or not. Doing so will probably cause more issues for you if the car runs well (and passes emissions, if applicable) otherwise.



Another thing that is happening is that the accelerator cable seems to be sticking. I have a fast idle sometimes 1500-2000 RPM, and I can get it back down to 900-1000 by pushing on the little arm by the microswitch (see arrow below). I see there is a spring there - maybe it's bad? Or something else is causing it to stick?

Disconnect the butterfly valve from the throttle spool (detach that little arm), then see if the valve is getting hung up. This will at least tell you whether you need to debug the valve/spool or the pedal cable (or its spool).



Even when I make sure to push it first and then turn off the engine, I still have the hot start problem. If I try to restart after a couple of minutes, it runs really rough for a few moments. If I wait more than five minutes, it won't start.

Giving it more throttle isn't going to affect the hot start problem at all. You need to find out what is leaking (and thus releasing the pressure). Fix that, then you'll be set.

Good luck.

Travis

[David T]

Before messing up any adjustments do the plug swap when you are trying to restart the motor when it is hot. If that gets you going you have a rest pressure problem. No amount of adjustment is going to fix it. You have to find and fix whatever is causing you to not hold up rest pressure. Could be fuel leaking externally, could be a bad accumulator, a bad fuel pump check valve or a leaky primary pressure regulator. No way is it going to be an out of adjustment mixture screw. Make sure you plug the hole in the housing above the mixture screw. If the 3 mm allen wrench won't fit, you have a big problem with the mixture unit. Don't turn it, it is a VERY sensitive adjustment and if it does need to be moved, 1/8 of a turn is a LOT!
David Teitelbaum

[aludden]

OK, I won't mess with the adjustment at all.

As far as the throttle, there's about 1/8" play on the little arm, and that is enough to make it jump to 1500-2000 RPM. Pushing it down makes the RPM OK, and it stays there. The throttle spool doesn't even move at that point. So I guess that spring on the little arm isn't doing its job. When I give it gas and let go, it comes back to the spot 1/8" away from the switch.

[opethmike]

OK, I won't mess with the adjustment at all.

As far as the throttle, there's about 1/8" play on the little arm, and that is enough to make it jump to 1500-2000 RPM. Pushing it down makes the RPM OK, and it stays there. The throttle spool doesn't even move at that point. So I guess that spring on the little arm isn't doing its job. When I give it gas and let go, it comes back to the spot 1/8" away from the switch.

I had the same issue with my throttle spool when I had K-Jet. I solved it by taking it apart and lubricating everything with all purpose grease.

[Bitsyncmaster]

Check the cable clamp on the valve cover holding the throttle cable. Mine had worn through the sheath on the cable and then the metal rusting caused it to stick.

[aludden]

Since the play exists without the throttle moving, I unhooked the little ball on the QUADRANT 102555 and backed it up a turn. Now I'm down to 1200RPM. There's still some play, so I will back it up another turn and see what happens.

Thanks!
Alex

[David T]

The link between the throttle spool and the throttle arm is called the quadrant link. It has 2 rod ends on it and they are threaded left and right hand so you do not need to undo an end to adjust the length, just loosen the two lock nuts and turn the rod like a turnbuckle. Lubrication can help but once the ends are worn all you can do is lengthen it so you push the throttle arm all the way to idle. You will have a little lost motion when you step on the accelerator pedal. BTW, there are pins in the rod ends just like on the struts so do NOT try to remove the ends unless you remove the pins first! You should consider lubricating the entire throttle system. This will have zero effect on your hot restart problem though.
David Teitelbaum

[Ratrace427]

In your description i got a little confused. When you changed your accumulator you are referring to the can under the car?

[aludden]

In your description i got a little confused. When you changed your accumulator you are referring to the can under the car?

Yes, that's the usual culprit in hot start problems. Interestingly, it's #39 in the parts manual, but it skips from 38 to 40... Anyway, this is the part: http://store.delorean.com/p-6548-fuel-accumulator-new-old-stock.aspx

[jawn101]

In your description i got a little confused. When you changed your accumulator you are referring to the can under the car?

I also sort of get the impression from the word 'can' that there could be confusion between the accumulator (http://store.delorean.com/p-6548-fuel-accumulator-new-old-stock.aspx) and the filter (http://store.delorean.com/p-6536-fuel-filter.aspx)

The accumulator is inside the center tunnel of the vehicle, near the shift mechanism. This is the one that is frequently implicated in hot start issues. The filter is on the driver's side, towards the rear of the car, nearer to the engine bay and under the trailing arm shield.

[aludden]

OK, I tightened the quadrant link, and now I'm idling normally.
I guess I should still lube the throttle cables (I have two, since it's an automatic). Is it an easy or nasty job? I guess I need to pull both cables out? Clean them and lube them with what?

[opethmike]

No, you don't need to remove the cables. There is a small circlip at the top of the spool that holds it assembled.

Remove that, and take all of the little pieces apart (while leaving the cables attached), noting how they go together. Then lubricate everything liberally with lithium grease.

When I was running the stock K-Jet setup, I had that problem of the spool not fully returning to idle. Taking it apart and greasing it up solved it, and kept it solved for the four years I ran that stock spool.

[aludden]

No, you don't need to remove the cables. There is a small circlip at the top of the spool that holds it assembled.

Remove that, and take all of the little pieces apart (while leaving the cables attached), noting how they go together. Then lubricate everything liberally with lithium grease.

When I was running the stock K-Jet setup, I had that problem of the spool not fully returning to idle. Taking it apart and greasing it up solved it, and kept it solved for the four years I ran that stock spool.

Thanks! I will do that.

[aludden]

OK! Back to my hot start problem...

Guess what? It seems I have been running without a check valve! Hervey tells me the car will not run without it, but ...

I bought a fuel pump from Hervey 3 years ago, and had a mechanic install it for me (I know... I know... I was desperate). Hervey's new fuel pumps with the external check valve need a dome nut instead of the hollow bolt. However, I didn't get that nut, so I believe the mechanic just installed it without the check valve. It fits. It works. Except of course it won't start when hot.

I was starting to doubt whether I had a new fuel pump at all, but it looks just like Hervey's minus check valve, and sure enough when looking through some old parts in a box I found a part that looks just like the check valve I just got from Hervey (always wondered what that was!).

So, am I way off? Will it run without a check valve? I'm about to try and put it together, but figured I would ask first.

[Bitsyncmaster]

I think the engine should run fine without the check valve. But of course you will have hot start problems.

[DMCVegas]

Absolutely your car will run without a Check Valve. Here is the quick and dirty explanation of things:

K-Jetronic Fuel Injectors have spring-loaded Needle Valves. So unlike EFI injectors in modern cars that can open at any fuel pressure thanks to an electronic valve, K-Jet relies soley upon pressure. Increase the line pressure, the valves open wider to feed more fuel. But to get them to open at all, you do in fact need a minimal pressure.

However when the engine is cold (below 54°F), the Cold Start Valve will open. This is in actuality a gigantic EFI-type valve whose purpose is to enrich the fuel mixture when the engine is cold in order to facilitate a "Choke" condition for the engine. On a warm, idling engine if you were to trigger that valve, the engine would flood and die within a couple of seconds. It really does dump that much fuel into the engine.

So on a cold engine with K-Jetronic that has a line pressure leak, you're essentially carbureting the engine in order to get it to run. It will sputter and run rough, but it will run. All the while the fuel pump is running and building up Line Pressure. Enough so that as the *carbureted* air mixture provided by the CSV runs out, the Fuel Injectors will begin to crack open as their pressures rise and will thus take over the duty of feeding fuel into the engine.

[aludden]

That's what I thought. Thanks!
Actually, it's been running beautifully without it, except for the hot start.
Now I need to find an acorn nut. I looked locally but all I could find was Hervey's alternative: a lug nut. However, I tried that and it leaked, so that's no good.
Thanks!
Alex

[Bitsyncmaster]

That's what I thought. Thanks!
Actually, it's been running beautifully without it, except for the hot start.
Now I need to find an acorn nut. I looked locally but all I could find was Hervey's alternative: a lug nut. However, I tried that and it leaked, so that's no good.
Thanks!
Alex

You will need the copper washers with the acorn nut. I it is just a lug nut but you need to find the correct size and thread.

[aludden]

You will need the copper washers with the acorn nut. I it is just a lug nut but you need to find the correct size and thread.

Yes. The problem with the lug nut I found is that it is not really a solid piece. It looked like it, but the cap part turned out to be really a cap, so once the pump built pressure I could see it bubble around the edge of the cap. I just went to other auto parts stores, and all they have is the same style lug nut.

I will try tomorrow in a serious fastener place... There is also a Volvo parts place, but our pumps are not really Volvo parts, are they?

[DMCMW Dave]

I can confirm that a car will run without the check valve. We had one come in like that with exactly the same issue. I've also seen a car come in with (solid) lug nut for the dome nut. It is tall and puts significant stress on the rubber cover but it will work. After a laugh or to we changed it to the correct nut. I believe the car we saw like that was completely missing the cover as well.

[DMCVegas]

Also, don't forget to AVOID reusing old copper washers and simply buy new ones. Aluminum will work, but you MUST use new ones. Otherwise you risk a leak and serious fire.

[aludden]

Yeah, it's fixed!!! :partyhat:

I found the domed nut (not easy!), installed, checked for leaks, readjusted the fuel pump height so the wheel well cover fits, checked for leaks again, and it works!

Thanks for all your help!
Alex

[Ron]

Yeah, it's fixed!!! :partyhat:
Just wait until you see how it runs when you tune it up now...

[kings1527]

My recent experience is related to this and hopefully it'll help someone out down the road who's reading this thread. I thought I had an accumulator issue (7 years old as of this post) because I'd have a fairly consistent hot start problem about 30-45 min or so after shutdown. Viton external check valve in place, new DMCH fuel pump/sender combo, new Viton o-ring in the primary pressure regulator...all good. So I was thinking it HAD to be the accumulator.

After a round trip of about 250 miles in one day, for some reason this problem started. Later on after researching this problem up and down, I looked at the mixture with my dwell meter and I was pretty lean. I made the adjustment (absolutely MUST be done with a meter) to put it back in spec and all seems to be well. But it was interesting how something as simple as that can definitely mimic a rest pressure problem.

Happy :driving1: