[7T3440CHARGER]

The SBEC is probably ok at this time.. When and if it fails, the truck will not start, no voltage would be at the coil for spark, or the charging system will be inop as the voltage regulator is built in to the SBEC. When the truck stops again, a simple test can be performed, unplug coil wire and have someone crank the engine.. Check for spark, if no spark is present, unhook the 2 wire connector at the base of the distributor. If you place a piece of wire in the female terminal on the harness end of the 2 wire connector, intermittently touch the wire to ground, spark should emit from the coil wire. This tests the SBEC to the pickup connections and internal SBEC for proper operation. More than likely you have the beginning of a pick up failure. These symptoms will continue until it goes completely, and, can continue for months.... In the early 90's this was a common failure in Dodge trucks, Dakota's and B vans.......

 

[Bob Lincoln]

I just realized, with the 3.9L V-6, we have the old problems of the worn-out timing chain guide, and also the bad distributor bushing. Have you replaced either one of these? How many miles on the truck? Normally they're shot between 100K and 150k miles.

 

[av8r115]

Looks like I need to go ahead and replace the pickup and coil. Sounds like that would not only fix the problem w/ the engine quiting, but would improve my MPG as well. Money well spent.

The truck just crossed 220K miles on it. Given the condition of the truck when I got it, I'm willing to bet neither the timing chain or distributor bushing have been replaced.

 

[7T3440CHARGER]

Pickup plate is usually less than $75.00 for OEM.. Use a quality part, not a big box auto parts special.... If the coil is original, look for oil leaks at the coil wire terminal, sealing edge at the housing and at the wire lug terminals. If oil seepage is present replace the coil. Set ignition timing on your V6 at 12 degrees before TDC for better performance and fuel economy.. I've worked on these engines since they came out in 1987 in the dealership and have owned a few as well. The last one I installed had to be obtained aftermarket as the manufacturer no longer serviced the plate. You will have to remove the distributor to properly install the pickup, you can check the drive gear once the distributor is removed for excessive "Feathering" of the gear. This will indicate dist. drive gear wear. This was a common issue in the later fuel injected Magnum motors, not carb equipped 3.9's.

 

[av8r115]

Pickup plate is usually less than $75.00 for OEM.. Use a quality part, not a big box auto parts special.... If the coil is original, look for oil leaks at the coil wire terminal, sealing edge at the housing and at the wire lug terminals. If oil seepage is present replace the coil. Set ignition timing on your V6 at 12 degrees before TDC for better performance and fuel economy.. I've worked on these engines since they came out in 1987 in the dealership and have owned a few as well. The last one I installed had to be obtained aftermarket as the manufacturer no longer serviced the plate. You will have to remove the distributor to properly install the pickup, you can check the drive gear once the distributor is removed for excessive "Feathering" of the gear. This will indicate dist. drive gear wear. This was a common issue in the later fuel injected Magnum motors, not carb equipped 3.9's.

My cash on hand only covers the big box stores - O'Reilly's in this case. Not my first choice, but they are within walking distance so that's where I bought a fuel pump and filter that I'm going to exchange for the pickup. Haynes indicates the pickup can be replaced by removing the distributor cap and rotor. Is that not correct?

On the coil, there's no oil seepage at all from any of the posts, so am I safe to keep using the old coil?

 

[Bob Lincoln]

Looks like I need to go ahead and replace the pickup and coil. Sounds like that would not only fix the problem w/ the engine quiting, but would improve my MPG as well. Money well spent.

The truck just crossed 220K miles on it. Given the condition of the truck when I got it, I'm willing to bet neither the timing chain or distributor bushing have been replaced.

Won't do any good to replace the pickup if you don't also replace the timing chain and guide, and the distributor bushing. There will be slop and wobble that will make the pickup intermittent or make it hit the shutter. It's possible that the pickup itself is still good, along with the coil.

 

[7T3440CHARGER]

Agreed, yet the bulletin Chrysler published is for the Magnum engines. This is a pre Magnum truck, drive gear wear is not inherent in the early engines, timing chain wear will not create a stall, heat soak, no start issue... TSB 18-08-93 dates to 1993 and up.

I could be wrong on this one, but have done this professionally in the Dealership since 1978.. quite a common problem..

 

[Bob Lincoln]

1992 is the start of the Magnum, my truck died because of this, at less than 100K. True, there is no fuel injector sync, but the ignition can cut out. And timing chain wear on these engines does pre-date the Magnum. Regardless, at that mileage, there WILL be slop.

 

[7T3440CHARGER]

Early 1987 requires removal of the reluctor on the distributor shaft to get to the plate. Later 87 models had a plastic plate that did not require reluctor removal..

 

[av8r115]

I know there's at least some slop because the last time I checked the timing it tended to jump around a couple of degrees. The question is whether it could cause the engine to quit?

It's stopped raining, so I'm going to check the resistance on the coil.

 

[7T3440CHARGER]

Due to current mileage, some slop is normal. As long as the timing mark does not jump 10 to 12 degrees when checking the timing you should be ok. Mine has 300k, the timing jumps about 5 degrees when checked with a timing light.. It runs almost as good as it did in 88 when I bought it.. almost......

 

[Bob Lincoln]

Problem is, it's not only the rotational slop, but the side play that will kill your ignition. As that bushing wears, the distributor shaft wobbles. This in turn causes the gap between the reluctor teeth and the pickup coil to vary, which changes the field strength and makes the ignition triggering intermittent. Back in the 1970s it was not uncommon for the reluctor to loose a tooth or shear off the pickup, then the car would just die.

 

[av8r115]

I can't get a decent reading off either the old or new coil. I'm using a regular Radioshack multimeter, not an automotive tester, but it should still be able to test resistance, right? I do get a continuity tone from both the primary and secondary coils (positive to negative, and secondary to negative).

 

[Bob Lincoln]

Primary coil resistance should be less than about 1.3 ohms, typically about 0.8 to 1.3 ohms. That's across the primary - the positive and negative terminals.

Secondary coil resistance is from center tower to the primary positive terminal. Should be between about 11K ohms and 13 K ohms.

http://www.aa1car.com/library/ignition_coils.htm

 

[av8r115]

I can't get any reading at all. Is there something significantly different about an automotive meter as opposed to my household Radioshack meter?

 

[Bob Lincoln]

No. Do you have the old cylindrical shape coil, or the newer square one that bolts up to the front passenger side of the engine? The older has ring tongue terminals to the primary, the newer one has a modular 2-wire plug. The terminals on the older one are much easier to probe, but you should be able to get in to the newer one. Is this a digital or analog multimeter? Is it set on the right range for resistance?

 

[av8r115]

Digital meter w/ auto range. I tried in auto-range mode as well as all the different ranges. The coil is an old cylinder style. When I first attached the leads, the reading bounced all over the place, then went to no reading at all. That's on both primary and secondary coils.

I have to work in 2 hours, so I can't mess with it anymore today. The engine runs for now, so I'm just going to return the pump, filter, and coil. Still don't have a solid answer as to what the problem is, but I'm out of time and I can't afford to stick it in the shop and let an expert figure it out.

 

[Bob Lincoln]

Does no reading mean the display is blank, or does it mean infinity (open circuit)? If the latter, then the coil is open and is bad.

 

[av8r115]

It jumps around and then goes to 0.00. The engine runs, so the coil is working. Is there a way to test the tester?

 

[Bob Lincoln]

Simple household test. Take an incandescent bulb that has cooled off and measure across its contacts (between the threads and the center contact). When cold, should be about 0.5 ohms or so.