View Full Version : 3.8 SC quits out of the blue then refires soon after,,,Help!

08-30-2015, 08:17 PM
Hey guys recently joined the forum.
Back in 06-07 I installed a 1989 3.8 SC 5 speed in my 64 Comet and have enjoyed it immensely!
Recently it developed a problem of quitting for no apparent reason. It will quit cruising down the road
with no load, let it sit for a few minutes and it refires instantly. It always runs great, gets good mileage
and makes great power otherwise,, any ideas where to start or threads to read up.
I'm a decent fabricator but no electronic skills

08-30-2015, 08:21 PM
You should have skills enuf to connect and use a code reader, no? ;)

Does the tach jump? Does it take more than one try to get it running again?

Might be cam sensor, but could be something else and/or a combo of things.

Nice looking engine bay, BTW.

08-30-2015, 08:52 PM
Thanks for the reply KMT
Well yes I need to get a code reader for sure.
I don't have a tack wired into the system.
When it's ready to restart it fires right up otherwise just turns over without attempting to fire.
Thanks on the engine bay note, it's an older photo have made more updates since then but
couldn't find a photo of it to post.

08-30-2015, 09:21 PM
i'm having the same problem. Mine is not throwing codes either. I've tried everything I know

08-30-2015, 09:28 PM
Thanks for the reply KMT
Well yes I need to get a code reader for sure.
I don't have a tack wired into the system.
When it's ready to restart it fires right up otherwise just turns over without attempting to fire.

What does 'ready to restart' mean? If it takes two or three tries, that's the EEC substituting default lookup values to let get it to at least run in limp mode.

Do you have a check engine light? Do you have the stock multi-wire ignition switch that normally sits down on the right of the SC's steering column?

Without codes, you risk throwing $$ money at it but oh well - cam sensor, crank sensor, bad/compromised grounds, bad/compromised (damaged/oiled/corroded etc.) harness/connectors/shielding, low volts, failing EEC, combo of any just listed. I'd start w/cam sensor, being careful to inspect front/upper harness while in there.

Good luck.

08-30-2015, 11:06 PM
KMT, by "ready to start" I mean that when I attempt to start it, it either starts or just turns over without firing at all.
It has never run in a "limp mode" as I understand the term,(decent enough to get you somewhere) it runs perfect as
soon as it starts.
No check engine light, stock 64 Comet gauges with their senders installed in the 3.8, oil, water, temp. stock 3.8 boost gauge in Comet.
I don't have the T-Bird ignition switch, A mechanic that is good with these electronics powered a couple of leads to computer through the Comet ignition, which have been problem free for years.
I forgot to mention right off the top that it is more prone to happen in the heat of the day, but has done it once in the evening recently, the problem is happening more often lately.
I modified the wiring harness length to fit into the Comet better keeping the shielding in place best I could and once again wasn't a problem for several years.
I will check all the grounds and clean any soiled areas of the harness and get a code reader for startrs.
The biggest problem is I may have to drive the car for days or hrs at a time to see if it will quit.

08-30-2015, 11:11 PM
I can't really weigh in on your situation other than to add that it could be what has already been mentioned--a ground may be your problem here, seeing as that it can shut down all the electrical accessories and fuel pump, etc. I had that happen on my Mustang, but thankfully I was a block away from home. It was pretty freaky, because the car just shut down, it wasn't like it sputtered out or anything. Edit: get your fuel pressure checked, too. Though it didn't happen on my Bird, I had a bad fuel pump on one of my other cars, and when it was up to operating temps and under load (even idling at less load in traffic), it would intermittently have power problems (felt like a compression problem) and would buck and shake and stutter. The problem is with the dying fuel pump, it would act up at the worst times, and then would be fine (ie: at the mechanic's shop, where they thought it was fine), and when the car was at operating temps, it would be harder to start up, until the car had cooled off a little bit.

Nice build, by the way! Have you run your Comet at the track? Or do you know how fast it is in a 0-60 or something? I'd imagine that it would haul buttocks, because Comets weigh significantly less than a Thunderbird SC does. I've always loved Comets and Falcons.

08-30-2015, 11:30 PM
Thanks for the comments 1FSTBRD.
The fuel pump will prime if I turn the ignition off and back on as soon as the issue happens making me believe
fuel isn't the prob.
No I've never run the car at a track with this combo (used to run a 351C 4speed at the drag strip in the 70's,,,, ya I've owned the car for over 40 years!)
But a friend of mine has a 2013 300 horse V6- 6speed Mustang that I can almost stay with. Probably could run with him if I had a better gear in the car, 3.0 gears and 275-60 tires,, maybe not the best combination,,,LOL

sam jones
08-31-2015, 01:28 AM
Good evening

Inspect the DIS harness. Check for indication of "brittle" wiring on either end of the DIS and or CAM connector(s). If you have access to a spare swap it. Heat can sometimes play havoc on this harness.

Good luck

08-31-2015, 12:37 PM
>it either starts or just turns over without firing at all.

That's the computer...if it fails to get input from, say the cam sensor, it will ignore that input and plug in a default value so the car will run. It should fire after 3 attempts (key still 'on').

>it runs perfect as soon as it starts.

It may feel that way, but the default tune in effect at that point is just that...a basic tune to let the engine run until the problem is rectified. 'limp' mode means limp to the dealer...not run run limp :)

Acting up when hot is typical of failing sensors, DIS and/or compromised harness/connectors.

You have classic/well known symptoms, requiring typical steps to fix.

Can you share a very recent photo of the engine bay - engine top/front?

Mike Puckett
08-31-2015, 02:53 PM
I don't see where anyone mentioned crank sensor but it could cause all of your symptoms. If you put a used OEM harmonic balancer on it, it may have broken. My original balancer would cause the engine to stall several times for a couple of weeks before it broke completely. It's worth checking or maybe just swap out the crank sensor to see if it fixes the problem.

09-01-2015, 11:35 AM
KMT, thank-you for your detailed answers! I will follow up on these ideas and report back.
Too bad I didn't know your in Salem earlier, Went through there with the car a nd our little camper Jan 14
on our way to a California winter holiday, pic on the beach Carsbad CA.
The attached is the best engine bay pic of the junk phone pics I have,,,lol

Mike, I replaced the balancer with a ?Dorman OEM style balancer prior to the problem.
Actually, installed a rebuilt long block at the same time.

09-01-2015, 12:30 PM
I love those! From the front end they look like a baby Continental. How is the 3.8 in terms of power in the Comet?

10-15-2015, 10:10 AM
Sorry for not reporting back on progress with every ones input.
I went through all the grounds and unit mounts then lost a wheel bearing which ruined the axle!!
I replaced that and drove it, same prob.
I didn't have the correct heat transfer material under the DIS so I had to order from Radio Shack by the time I got it the insurance ran out so I won't be driving it till next spring now.
Thanks again for the input and I will continue the search in the spring.

10-15-2015, 08:59 PM
honestly those dorman balancers are junk, ive drilled three of them off the end of my crankshaft now and finally gave in a bought the good one from supercoupe performance. seriously, its expensive but just do it.

10-15-2015, 09:24 PM
Sorry to hear, Fred. Your Comet is beautiful--love the tires/ wheels, and I would love to see the looks of confusion when you lift the hood at the car shows. The cool thing with that engine, is that you're getting great gas mileage for a great cruiser, but with great power and torque. Other guys with big stroked out engines and things like that often make the cars race ready, but the cruiseability suffers. The small but high powered V6 engine seems like a natural choice for a small, economical car......if they built the Comet with a high powered option in the late 80's, you'd think that the supercharged 3.8 would be a consideration from the factory.

10-04-2016, 01:02 AM
Well I finally got the car out of the garage to try the fixes several of you have offered!!
I replaced the DIS module and the heat transfer grease under it.
drove it about 200 miles today under several conditions with 0 problems!
A lot has happened this year and never really got to the Comet till just lately
Thanks to all those who offered ideas.

10-04-2016, 08:16 PM
It is always great to hear when someone gets their SC engine up and running, man. :D

10-09-2016, 08:08 PM
That is a very cool car man!!! Awesome job putting the SC motor under the hood, car looks great and glad you got the problem solved!!!