Won't start after sitting

[centauri]

Owned this car for 3 years but don't know the recent service history; 80K miles, been to Garden Grove a few times, clean and original and always garaged. It has had this starting problem since I bought it, and so did my previous D, so I thought it was just a DeLorean thing. But from reading the forum it sounds like a well-running car shouldn't be like this. I am capable of most basic repairs, but no idea how to diagnose.

If I've driven the car within the past two or three days, it will start up cold right away, and will start hot, warm or cold all day from there. But whenever I leave it sitting for say 4-5 days or more, it will just prime and crank without catching. This time it was only sitting 4 days. I always keep the clutch depressed, leave the key for a moment in each position before starting, and I hear the fuel pump prime like always. I don't crank for more than 8-10 seconds, and I don't touch the gas pedal. The battery is good and fairly new but I leave it on a Tender just to make sure. I tried the CSV plug swap but I don't think fuel is the issue as I normally smell a little fuel there after one or two tries. I'm guessing that hearing the fuel pump prime should rule out the inertia switch.

If I try and it fails, I let it sit for a day and chances of starting improve, but sometimes it takes until the 3rd day. When it does finally catch, it does so after a only a few cranks and starts right up, the usual idle hunting then smooth idle and plenty of power.

This is at least the third time this issue has kept me from attending an event, because I forgot to begin the starting ritual in the days prior.

Are fuel problems ruled out yet? Fuel filter maybe? And if not fuel how to diagnose spark - and why would spark be a problem if it runs fine otherwise. I have a brand new coil I could try swapping in but don't want to waste effort.

Doug
#2259 "2RYLOS"

[Bitsyncmaster]

My guess would be your CSV is not working. Did the "plug swap" seem to help? My car if it sets for a week or two will need the CSV to get it started but never needs is otherwise. My CSV only works if the engine cranks for more than one second so I know when it needs it.

[Ron]

When it fails to start, pull the easiest plug wire you can get to and see if it has spark. Hold it ~1/4" from the engine block (or use a spare spark plug, grounding it on the block) and look for spark while a helper cranks the engine over. If you have spark then, it may simply be flooding, especially since you say you smell fuel...Maybe try cranking it without letting it 'sit a moment in each key position' to avoid a leaky injector or the CSV from dumping fuel.
It sounds like it could stand a basic tune up in any case.

[DMC5180]

This does not sound like the classic HOT START issue. Usually those will start after a few hours of cool down. Several days is unusual.

This kinda sounds like your Ignition resistor BY-PASS is not functioning. (Weak spark during cranking). Wiggle the spade terminals to see if they seem loose. Check Coil connections. Verify the wires are on the proper coil terminals. Use the ignition Diagram found in here for reference.

http://dmctalk.org/showthread.php?40-All-Wiring-Schematics.

[Ron]

Direct link (http://dmctalk.org/showthread.php?40-All-Wiring-Schematics&p=66530&viewfull=1#post66530)

[DMC5180]

I'm surprised the the POS and NEG are not indicated for the coil connections on the schematic. Makes a difference as Dave S. can tell you about a car that came in the shop with the coil turned around in the bracket and wired backwards.

[Ron]

I didn't mark the coil wire (+) since it is the only one in that harness that goes to the coil...
(FWIW- at the coil, the ends have different size eyelets)

Edit: I see you were talking about the other schematic...(Dave's must have been butchered)

[Bitsyncmaster]

What I think happens is the injectors leak very slowly so the lines to the injectors get drained. When that happens you need the CSV to get the engine turning over fast enough to get fuel flowing to the injectors. Could also be the FD leaks very slowly but the result is the same.

[DMC5180]

I didn't mark the coil wire (+) since it is the only one in that harness that goes to the coil...
(FWIW- at the coil, the ends have different size eyelets)

Edit: I see you were talking about the other schematic...(Dave's must have been butchered)

Yeah, but that didn't keep somebody from doing backwards at least ONCE :biggrin:.

I thought those are spade terminals attached to Ring mounted tabs. Although now that I think of it. Isn't one of the tabs Female and the other Male?

[Ron]

Yeah, but that didn't keep somebody from doing backwards at least ONCE :biggrin:.

I thought those are spade terminals attached to Ring mounted tabs. Although now that I think of it. Isn't one of the tabs Female and the other Male?
Damn it...now I have to go to the shop and look...

[DMC5180]

What I think happens is the injectors leak very slowly so the lines to the injectors get drained. When that happens you need the CSV to get the engine turning over fast enough to get fuel flowing to the injectors. Could also be the FD leaks very slowly but the result is the same.


Yeah I just re-read the OP. Somehow I mis-read it. I was thinking it needed to sit several days BEFORE it would start again. I think your on the right track Dave. Leaking down Injector(s). I get a little bit of that myself after long periods of non-operation. It never fails to start even if only on 3 cylinders for few seconds till the lines purge air out and the Idle stabilizes.

[John U]

Try priming with the key 3 times before starting....let us know if that works

John

[DeLorean03]

Regarding the ignition coil's polarity, I would think that the side that has two wires - one of which goes to ground- would be the negative terminal. Just a guess, as I am not at my car right now (at work on base).

[David T]

I would check the Thermo-Time switch. See if it starts with the plug swap and that will tell us if it is fuel related. "Leaking down" injectors has nothing to do with it, it should start on the CSV and that requires very little pressure. After a couple of hours you have lost rest pressure no matter how tight your system is. By then the CSV should run again during starting.
David Teitelbaum

[kings1527]

I would check the Thermo-Time switch. See if it starts with the plug swap and that will tell us if it is fuel related. "Leaking down" injectors has nothing to do with it, it should start on the CSV and that requires very little pressure. After a couple of hours you have lost rest pressure no matter how tight your system is. By then the CSV should run again during starting.
David Teitelbaum

Would bypassing the thermotime switch with a jumper wire be a good test for this problem? I think inserting a wire in the BLUE/black wire side of the plug on the thermotime switch wiring and then grounding the other end accomplishes that.

[centauri]

Thanks all for the great suggestions! I have tried the plug swap to no avail as well as jumping the thermotime. Once it doesn't start that day, it won't start until it's sat for a day, and with the strong fuel smell I'm starting to suspect flooding due to weak initial spark. You've given me lots of things to try, will update the thread when I find out more.

[Bitsyncmaster]

Would bypassing the thermotime switch with a jumper wire be a good test for this problem? I think inserting a wire in the BLUE/black wire side of the plug on the thermotime switch wiring and then grounding the other end accomplishes that.

You can bypass the thermotime switch with a jumper in the "hot start" relay. But you still have all the other wiring and even the possibility of a bad CSV (rare failure rate). Thermotime switch failures are pretty common. Sometimes they even fail leaving the CSV running all the time (Have seen one fail like that). My car had a bad connection in the bulk head connector on the CSV.

[Ron]

It never fails to start even if only on 3 cylinders for few seconds till the lines purge air out and the Idle stabilizes.I can see the pressure dropping off, but how could it go negative and cause air to get into the lines?


Regarding the ignition coil's polarity, I would think that the side that has two wires - one of which goes to ground- would be the negative terminal. Just a guess, as I am not at my car right now (at work on base).The positive (+) side has the White/Yellow, from the resistor, and a Yellow, to the capacitor. The negative (-) has a White/Slate that goes into a harness and eventually branches to several places.


Thanks all for the great suggestions! I have tried the plug swap to no avail as well as jumping the thermotime. Once it doesn't start that day, it won't start until it's sat for a day, and with the strong fuel smell I'm starting to suspect flooding due to weak initial spark. You've given me lots of things to try, will update the thread when I find out more.
If you suspect too much fuel, check for wet plugs immediately after it fails -- It may pay to look at them after it has sat for days but before you ever turn the key on.....or unplug the CSV before you even try.

IMHO the plug swap is good for a quick check or if you are out on the road, for several things. But if the question is lack of fuel, it's better to use a shot of ether and eliminate many things at once.

[David T]

If the plug swap didn't work that leads me to ignition. You need to see if you have spark the next time it won't start. The fuel smell could be because all of the fuel being supplied to the motor is not being burned because there is no ignition. No ignition could be because of a bad ignition coil or a bad impulse coil (the 2 most likely components to fail). Could also be a bad connection like on the ballast resistor. Clean them up.
David Teitelbaum

[DMC5180]

I can see the pressure dropping off, but how could it go negative and cause air to get into the lines?

Yeah , I know. (finger on the straw should hold the liquid).

I had a mid 85 Audi Coupe with K-Jet and really bad leaking injectors when I bought it. After sitting for the day at work the lines would leak down completely. It always started quickly with CSV, but as soon as the shot of fuel was consumed it would nearly die, then it automatically fired the CSV again. The engine would rev up consume the fuel again then almost die again in an ongoing cycle until it ran smooth at stable idle. Depending how long it sat, it would take up to 5-6 cycles like this before eventually stabilizing. (I never touched the pedal either to speed the process) That car may have had a functioning Hot Start relay system because it would continue automatically ,almost in a timed fashion, re-firing the CSV cycle until stabilized. I never delved into that system to find out how it was different than the DMC system. I rarely had to re-crank the engine though. Eventually I got around to having those injectors cleaned and the problem largely went away for awhile. I remember the guy at the shop say they were pretty bad but he managed to get most of them to spray normal after the cleaning.

The last Time I had The intake off the D for VOD work a couple years ago. I peered into the intake valve ports and noticed liquid pooled on the closed valves. At first I thought it was oil or coolant. But after dipping a Q-tip in it I discovered it was puddled FUEL and the Injectors had been replaced with NEW the year prior.

[Ron]

The last Time I had The intake off the D for VOD work a couple years ago. I peered into the intake valve ports and noticed liquid pooled on the closed valves. At first I thought it was oil or coolant. But after dipping a Q-tip in it I discovered it was puddled FUEL and the Injectors had been replaced with NEW the year prior.
Reminds me of JimJam's problem. He had 3 brand new injectors that were bad. Two leaked way below spec pressure and one spewed rather than sprayed. As you may remember, most of us thought he had the classic D hot start problem at first since it was cold out and it liked the extra fuel when it had sat a while, but when when summer came around, the black smoke gave it away lol. (I'll never forget it being 90F+ at 3AM ;-)

[DMC5180]

(i'll never forget it being 90f+ at 3am ;-)

ugh!

[centauri]

I cleaned up and checked all the connections to the resistor and coil, still no start. Next day I pulled a plug, no sign of damage, just grayish brown deposits. So I let it sit for a week, then with an event coming up I started the once-a-day attempts. On the third day still no luck, so tried installing the new coil from DMCH, no help, 2 days later no good. Let it sit for another 10 DAYS and came back with better tools. Confirmed 12V to the coil + post with switch in ON position. Hooked up an in-line spark tester to the back left plug and set my phone to record (no helpers) -- and it started up immediately.

http://youtu.be/1WZu4vNREZo

Removed the tester, started it a few more times, then went for a long drive to warm up, started again hot; cooled down for a couple hours and started again warm. Left it off the charger, started the next morning too, and each time nearly immediately, as if it never had a problem - back to square one. I guess I have to wait for it to fail again, but I'm at a loss to isolate the conditions that create this problem. Will try again in a few days. Phases of the moon? Cosmic rays? Or only on beautiful sunny days when I'm planning to drive it somewhere?

Another question - if I want to go ahead and replace plugs, wires, cap, can this job be done without removing the intake and fuel metering? This takes <1hr on a slant 6 but this looks like I will need intake o-rings, fuel crush washers, etc.