Ignition coil questions...

[Kenny_Z]

I was looking for vacuum leaks but didn't find any. I'm going to get something to spray a mist and try again tomorrow.

I was reading another forum about PRVs and this stalling issue. Unfortunately the thread didn't conclude with a resolution but it did give me things to try. Step 1, clean the idle motor. Step 2, check the throttle/butterfly valves for clogs. My intake was saturated with old oil I'm leaning toward this being at least part of the problem.

I compared the D's voltages with my Stang's and Red came out on top with slightly higher voltages. That surprised me as my old 289 runs extremely well with zero issues. I'm leaning further away from this being an electrical issue. I'm going to dig out my timing light tomorrow. I managed to misplace it at the beginning of the summer.

[Kenny_Z]

The new ground seems to have really helped. The misfire over 3000 RPMs is gone. On my test drive I pushed her up to 4500 RPMs in 3rd and didn't hear or feel any misfire or hesitation. She's starting a lot faster and the rich exhaust smell is gone. I'm pulling closer to 14 volts from the alternator now.

She didn't stall out on me completely but my RPMs are still flakey when pushing in the clutch. It only happens when she's warmed up. I don't have much of an idle hunt after the initial start up hunting. Once she evens out the rpms are solid until the engine is fully warmed up. It's weird, the voltage meter drops and if I have the headlights on they dim quite a bit. The RPM gauge goes up but the motor sounds like it loses RPMs. It sits like this for a second or so and then the voltage meter goes up, the RPMs sound like they return to normal, and the RPM gauge drops to between 700 and 800. Then about a second or so later it starts over.

I've got a replacement O2 sensor to install and I still have to clean the idle motor and butterfly valves. I may do the fuel accumulator replacement while I'm at it.

[dn010]

You should check the condition of your cap / rotor if it has been a while. It may be time to replace. Personally, I could never get my D to run decently on any coil other than the original one - there were always issues with higher output ones. If you have a stock one throw it back in and see if your issues persist, it is worth a shot.

[Kenny_Z]

I just replaced the cap and rotor with units from John Hervey. The old coil was cracked and ended up falling apart (literally) after it was removed. I do have a lower voltage coil from an old I6 Ford that I could try. Right now the priority is lunch

[content22207]

I know several owners, myself included, who are running true HEI with excellent results.

Bear in mind that ignition coil secondary voltage is directly proportional to its input. You can not run only 6-8 volts into a high winding coil and expect anything close maximum rated output (most HEI coils are rated at 12-14 volts input). You will get more secondary voltage than a stock Bosch coil simply by virtue of the higher number of windings, but certainly not anything close to 40,000 volts.

Bill Robertson
#5939

[ramblinmike]

I know several owners, myself included, who are running true HEI with excellent results.

Are you running 12v to the coil with the stock Bosch amp or the Duraspark you were running? I know guys run 12v to the Duraspark all the time.

[content22207]

I am running 12.5 volts into a Pertronix coil. Voltage is something like 8 or 9 volts to the Bosch ECU at the other end. I was only test driving a Duraspark unit for Byrne. He gave me his dead Bosch unit, which I will use to make another adapter to carry with me in case my ECU dies.

My resistor grid is wired in parallel (that is how I get 12.5 volts into the coil):
IgnitionCircuit.jpg
Pertronix coils can of course handle full charging voltage no problem. I only step it down for the ECU's benefit. I don't trust Bosch ECU's any further than I could throw one of the damn things. If I was running an original Ford Aerospace Duraspark ECU, I wouldn't reduce input voltage at all.

The biggest advantage of HEI is the ability to open up the plug gap. .026" is ridiculously small. No wonder stock DeLoreans run like crap. The benefits of wider plug gaps have been known for decades. Nearly every other manufacturer was already running .05" plug gaps when DeLoreans were new in the showroom. GM introduced HEI in 1971. DeLorean ignition was obsolete even before these stupid little cars were nothing more than a stainless steel fantasy in the back of JZD's mind. The man was vice president of the company that pioneered HEI, for crying out loud -- he should have known better.

Speaking of which: DO NOT OPEN YOUR PLUG GAP IF YOU ARE STILL RUNNING SUBSTANDARD DELOREAN 6-8 VOLTS INTO THE COIL, NO MATTER WHAT KIND OF COIL IT IS (can I hear an "Amen" Steve?). The stock resistor grid is really better suited for breaker points than breakerless ignition.

Bill Robertson
#5939

You can get away with smaller plug gaps in high compression and forced induction engines because the mixture is easier to ignite. Some owners claim that larger plug gaps are actually counter productive in those circumstances.

In a low compression engine, like the stock DeLorean PRV, the mixture is harder to ignite. Leaning the mixture out for fuel economy and emissions exacerbates the situation. That is one reason American manufacturers were so quick to adopt HEI in the early 70's.

A Society of Automotive Engineers' study from the time: http://dmctalk.org/showthread.php?65...ull=1#post7222
I found it particularly fascinating that wider plug gaps also yielded benefits similar to increased gap projection (you don't need to change spark plug length -- just open the gap up).

Bill Robertson
#5939

[stevedmc]

Speaking of which: DO NOT OPEN YOUR PLUG GAP IF YOU ARE STILL RUNNING SUBSTANDARD DELOREAN 6-8 VOLTS INTO THE COIL, NO MATTER WHAT KIND OF COIL IT IS (can I hear an "Amen" Steve?). 9

Preach on brother!

[content22207]

This is how crappy DeLorean ignition is: if you don't bypass one of the resistors, you can't even start the damn car. Who dreamed this stuff up -- it's stranger than fiction.

I've seen cars with one ignition resistor, but until I bought a DeLorean I never saw one with two.

Bill Robertson
#5939

[Kenny_Z]

I didn't get to spend a lot of time with Red today but I did get to clean the idle motor and the butterfly valves. Unfortunately the idle issue still remains but I did get a surprise from the car. When I went to crank her up I expected the usual 5 to 10 seconds of cranking before firing up but this time I had a split second start up. I had to look around and make sure I was actually in the Delorean. It may have been a fluke start up though.

Tomorrow I hope to do some more grounding. I'm using Bitsync and Bill's ideas as a guide. I think the chassis length ground cable and grounds for the inertia switch are both within my abilities to perform. The testing I did today was on a cool engine. When I turned on the headlights, A/C, or switched on the vent fans I got a severe voltage drop. Running all 3 at once made the motor sound like it was struggling to stay afloat. Grounding the engine better fixed the stalling and misfires but I think my current idle drop issues are in the accessories.