No Spark (kind of urgent help req'd)

[pieter]

Ok, I'm 60 miles from home. I do have another vehicle to use and the truck is sitting in a parking lot. I drove there this am and truck ran crappy as usual, but it was running. Go to start it up about 6 hours later and it just cranks and cranks. I smell gas, so I figure it's flooded. Granted, this is the throttle body injection.

Regardless, I pull a sparkplug and hold it to the exhaust manifold and I get no spark. Pull the distributor cap and the terminals are corroded. I sand those down and try again - No Spark.

Next two things, we have the coil and the module within the distributor. How can I check either device for a malfunction. I do have a volt meter and my full set of tools with me, so I can tweak on most things. I have no book for reference though.

Besides the coil and module in the distributor, is there anything else that can affect spark? Besides the ECM and I'm praying it is not the ECM... I don't believe this 1991 has a resitor module like the 70's trucks...

Basically, this is a dodge 1-ton 2wheel. Throttle body 360 automatic. If you've followed my other posts, I've been having issues with it running right and have error codes that I pulled earlier this week.

When I left the truck, I did pull the battery terminals to hopefully clear the fault codes from the ECM....

And yes, I did put the rotor back into the distributor.

Anyways, if you have some thoughts or suggestions it would be greatly appreciated.

Thanks,
Pieter

[712edf]

A 1991 model 360 should have what's known as a Hall Effect Electronic Ignition System (at least according to Haynes). This ignition system was used only from 88 to 91 (again citing Haynes) and used a distributor that contains a Hall Effect switch/pick-up. This distributor differs from a normal Electronic type distributor that Chrysler used from around 72 to 87. Also on the drivers side fender is a electronic computer "thingy" called a Single Module Engine Controller (SMEC), which runs fuel control and ignition timing both. The SMEC looks nothing like the 4 & 5 pin ECU's that we're used to seeing on the firewall/fender. I'm not sure if this SMEC is the ECM which you were refering to. If I were guessing first I'd replace the coil, then the Hall Effect pick-up in the dist, and finally the SMEC. I don't see anything else major that would kill the spark.

[pieter]

Thanks for that info. I was digging around this site: http://www.allpar.com/fix/index.html

and read about the Hall Effect thingy you mention as well. Trying to figure out what cheap things I can pick up at the parts store in the morning to try and get this truck running.

Drivers fender I only have two little electronic gizmo's. They are small like the size of a flasher or a little bigger then that.

Well, I guess I can take this info and try and attack Sunday afternoon.

Thanks,
Pieter

[712edf]

The connector going to the distributor shoud have 3 cavities (meaning the wire from the distributor has 3 pins). The top or #1 cavity should have almost full battery voltage when the key is on. If so hold the coil wire (high tension wire to the dist. cap) about 1/4" from a good ground, then run a jumper wire betweent the #2 and #3 cavities on the above mentioned connector. Then disconnect/reconnect this jumper wire a few times (likes points a firing) and see if the high tension coil wire has a spark. If spark is present and the #1 cavity has the proper voltage the problem should be in the distributor itself (Hall Effect pick-up,rotor,cap,etc).....I'm quoting this from a Haynes manual. I hope I'm not doing more harm than good.

[712edf]

[quote=pieter;68955]
Drivers fender I only have two little electronic gizmo's. They are small like the size of a flasher or a little bigger then that./quote]
These could be fuel pump relay, auto shutdown relay, starter relay, a/c clutch relay, torque convertor clutch relay.....If that auto shutdown relay went bad this would kill the spark too I think...The SMEC appears to be right by the drivers side headlight, but on the fender. At least that's where it is on the drawing of an 89 model in my Haynes manual #30040 page 6-37.

[JimmieD]

Hi Pieter!

Please e-mail me ASAP, I have a troubleshooting document to forward to you but it's far too big to fit in a PM.

jimmied@optech-center.net

Standing by....

[pieter]

Thanks so far -

I'm going to see what cheap parts I can pick-up at the auto store then go to the truck and see if we can get spark.

Pieter

[JimmieD]

By now you've received my e-mail. Just a guess, but I'd check the readings on the oxygen sensor first. Because of its position down on the exhaust manifold the wire is subject to damage, plus the sensor itself is a wearing part, being exposed to exhaust gases. A bad one can cause all kins of bizarre problems.

The computer is designed to go into a 'limp mode' which is a fail safe mode if O2 sensor fails. It's only enough to get the vehicle to a repair spot, hopefully, and shortly after it may well shut down completely.

[pieter]

The connector going to the distributor shoud have 3 cavities (meaning the wire from the distributor has 3 pins). The top or #1 cavity should have almost full battery voltage when the key is on. If so hold the coil wire (high tension wire to the dist. cap) about 1/4" from a good ground, then run a jumper wire betweent the #2 and #3 cavities on the above mentioned connector. Then disconnect/reconnect this jumper wire a few times (likes points a firing) and see if the high tension coil wire has a spark. If spark is present and the #1 cavity has the proper voltage the problem should be in the distributor itself (Hall Effect pick-up,rotor,cap,etc).....I'm quoting this from a Haynes manual. I hope I'm not doing more harm than good.

I tried this. I get close to 9 volts. Not sure if that would be considered full battery voltage. I get 12.4 volts at the battery. Off thing is when I jump this circuit, it starts squirting fuel down the TBI. No spark to off of the coil wire to distributor.

I also do not get 12v on the + post of the coil with ignition on. Should this be 12v? Do I need to crank the engine to see voltage on this post?


JimmieD, if the system shuts down completely how do you reset it or bring it back?

I forgot to see if it will give me error codes today. I'll go back to the truck and see what error codes it spits out.

Also, on the drivers side fender. I have 2 relays. One plastic, one metal. I'm assuming one of these is the Automatic shut-off relay. Can this be picked up at a parts store or checked? I see the check info from JimmeD's information I recieved.

I found the SMEC. It's buried behind the battery and seems to be in conjunction with the air intake tube system. I cleaned those connections out as well...

I'll see what error codes it is giving me and go from there...

pieter

[712edf]

The #1 cavity should be within 1 volt of full battery voltage according to the text, yet elsewhere in the same manual it shows a lesser amount, so the 9 volts your getting should do something....No you shouldn't have to crank the motor to get some coil voltage. But only while cranking will it be 12 volts, at least this is how it is on std. electronic igns.

[JimmieD]

Hi Pieter,

Did you receive that troubleshooting info e-mail?

The only way I know of to force a reset on this computerized system is to disconnect the battery cables for at least 5 miuntes. Then when you reconnect & restart or attempt to, it will toss the latest error codes when you access them. It will wipe all the old error codes, generate new ones, saying what's wrong now.

I have a 1990 1 ton Factory Service Manual here, if there's anything I can look up? I can also mail it to you & you send it back when you're done.

.

[JimmieD]

There should be 4 relay sockets on driver's side fender well, but on 1 ton truck one relay will be missing, so one empty socket, the last one closest to firewall. I believe the missing one is the Part-Throttle Unlock Relay, not used on your trans.

The other 3 relays, in order from firewall, should be A/C Clutch Cutout Relay, Auto Shutdown Relay, and Starter Relay. Auto Shutdown relay should be smaller than the others two.

Quoting from FSM:

The Auto Shutdown Relay [ASD] supplies battery voltage to the fuel pump, fuel injector, ignition coil, and O2 sensor heating element. The ground circuit from the ASD Relay is controlled by the SBEC Single Board Engine Controller [that's the computer on fender well front, behind battery]. The SBEC controls the relay operation by switching ground circuit on and off.

The SBEC monitors the distributor pickup signal to determine engine speed and computer injector synchronization. If the SBEC does not receive a distributor signal when the ignition switch is in the 'Run' position it will not energize [not provide a ground to] the ASD Relay, stopping the battery voltage supply to the fuel pump, fuel injectors, ignition coil, and O2 Sensor heating element.

Ignition coil:
The SBEC controls the ignition coil firing through the ASD Auto-Shutdown Relay. When the relay is energized by the SBEC, battery voltage is supplied to the ignition coil positive terminal. The SBEC will not energize the ASD relay until it receives input from the distributor pickup. Refer to the 'ASD Relay' in this section for relay operation.

The ignition coil is designed to operate withut an external ignition resistor. Inspect coil for external leaks & arcing.
Test coil according to coil tester mfgr. instructions. Any arcing at coil tower will carbonize the the secondary wire nipple. Installing the cable on a new coil will cause the coil to fail. [I read that as saying to check coil wire for signs of arcing, replace as necssary.]

.

[Paul in MN]

The other guys may be correct in their analysis, especially with the truck having the TBI and much more complicated electronic engine control.

But....just maybe it isn't the electronic stuff. My experience based on an 86 W250 360 gave the same symptoms. But I can start the truck by holding the auto shift lever just a hint into the "drive" position and wiggling it towards "neutral" while cranking. It will pick up "the message" and start pretty quickly. Now I assume this is a misalignment of the neutral safety switch due to under cab rust which has lowered the cab closer to the frame, thus the linkage is outta wack. Otherwise you can crank till the batt dies and the engine is badly flooded. The wierd thing about this sequence is that the truck needs this special starting technique for first start in the morning, but will usually start in normal "park" the rest of the day! That part I really don't have a clue about. The good part is that nobody is going to steal my truck first thing in the morning.

Good luck in getting yours going, I hope the solution is as cheap as mine was.

Paul in MN

[Hobcobble]

This same thing happened on my '90 D250 318 TBFI. It
turned out to be the computer module on the firewall.
I don't recall the exact price but it was approximately
$450-$500 at the time [going back 15 years or so...]
John

[pieter]

I'll give Pauls shot a try. I don't like teh new computer, although I'd go to a junkyard first. Trying to justify $500 for a computer that might not fix my issue is a chance I can't afford right now.

I've only got two relays as I don't have A/C on this vehicle. That would mean the plastic relay with the Automatic shutdown... The steel one is the starter relay.

I'll be back in a bit to see what I find out.

Thanks.