Dakota Forumz banner
1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hello,

I have a 96 Dakota, 4 cylinder, with an intermittent starting issue. It can be running great when hot, I shut it off, and then try to restart - it will not have any spark. When it fails there is NO spark from the coil , when it cools down (20 min wait time) the spark returns and engine starts. Any thoughts on what to check/replace?

The problem occurred once - two yrs later it appeared again, then last week, now it is everytime it gets to normal temp and I shut it down. I haven't done anything in either diagnostics or replacements yet. No codes from the ODB, no Check Engine light, etc.

I've been a shade tree mechanic since '59 and have plenty of experience in subtle troublesome intermittent problems, however this one has me stumped. Any help would be appreciated.

Frank
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #2 ·
OK OK OK, I started the shotgun approach to troubleshooting/fixing the problem; I 1st checked the dist cap, rotor and plugs & wires; no carbon tracks, no cracks, no noticeable wear, the wires are still pliable, not brittle, nor any cracks in the insulation, so I unplugged/replugged all the connectors and the replaced the coil - still fails, although the symptoms are altered; it restarts several times now when hot, before failing to start for the 20 min cooldown delay time.

Also there is a noticeable predetonation (soft backfire) occasionally while cranking prior to starting. When in the non-starting mode, the backfire occurs occasionally, ie, hiccups the smooth pattern of the starter running, but doesn't start the engine. I guess the next step is to replace the wires, dist cap and rotor, even though they don't appear to be the culprit. Then on to the Ignition module or if anyone has stumbled upon this problem before, please reply and save me the time/$s-Thanks
 

·
Registered
Joined
·
1,211 Posts
well your first post says there it no spark from the coil when it happens, so i would start there, not the rotor or wires
 

·
Registered
Joined
·
250 Posts
A bad crank position sensor would exhibit these symptoms and could be bad without throwing any codes. You'd need a lab scope to confirm this though.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
RamTech-Thanks for the insight, that was the problem, apparently it was a heat stressed 100K mile intermittent issue, so when it heated up, it failed, cooled down and regained functionality. Odd thing was that it only failed upon the STARTING, not only a heat run condition.

So with your input, I took a 2 liter bottle of water along, waited for the failure to manifest, then poured the cold water from alongside the back side of the carb so the water ran over the bell housing where the crankshaft position sensor was mounted. The cold water cooled the sensor and within 1 min it started-found at last! Then on to the Internet for the $70 part vs the dealer $150 part and it is back "on the road again"!

When replacing it, I noticed that the hall effect sensor in the assembly would trip the relay in the block of fuses under the hood (when the ignition key was turned on) showing the sensor was working, when I moved the sensor close to the bell housing, further away, close again, etc. I suspect that under the failure more (engine hot when stopped) the same action would not occur, however I did not want to go through all the effort with a hot engine, burning myself on the hot parts while I test this theory, after replacing the part and the problem was solved. It may be another test that may work, in addition to the pouring water over the part scenario to validate the problem, vs the dealer game of big bucks diagnostics, and ultimately move as much of my pile of money to their pile of money as quickly as possible.

Then months later I inadvertently overheated the clutch and bell housing going over the Grapevine near Bakersfield, CA (clutch slipping) and the housing the sensor was mounted on got hot enough to begin to deform the phenolic plastic sensor material. The same symptom showed up, I stopped the truck (actually the clutch wore so bad it did not make any contact with the pressure plate, guess the springs lost their k factor), shut down the engine . When I tried to start the engine again, no start. I waited 45 min for the tow truck, it started the engine fine. So the next morning I replaced the clutch, looked at the sensor, and decided to try using it as is since it again started the engine fine, and no problems since, working good 5K miles later, although I suspect I severely over-temp stressed the part so it will likely again begin to fail in the (hopefully not to) near future.

Thanks again for the key to finding the problem!
 

·
Registered
Joined
·
830 Posts
RamTech-Thanks for the insight, that was the problem, apparently it was a heat stressed 100K mile intermittent issue, so when it heated up, it failed, cooled down and regained functionality. Odd thing was that it only failed upon the STARTING, not only a heat run condition.

So with your input, I took a 2 liter bottle of water along, waited for the failure to manifest, then poured the cold water from alongside the back side of the carb so the water ran over the bell housing where the crankshaft position sensor was mounted. The cold water cooled the sensor and within 1 min it started-found at last! Then on to the Internet for the $70 part vs the dealer $150 part and it is back "on the road again"!
Long story, glad you found it. I had a similar problem with a 99 Dodge Ram
5.2L. It would start ok, run for a while (20 mins) then die like it was
not getting fuel. Tested the fuel pressure ok..no spark either.
Turned out to to be an intermittent cam sensor (Hall effect) that was
heat sensitive and decided not to work as soon as the engine warmed up.
Cooled down and it would start and run fine. No codes of any kind.

Never tried the cold water technique, but it's a lot more difficult to cool down
the hot engine when the sensor is inside the distributor cap.

So much for solid state electronics..thankfully these are mostly reliable. :D

When replacing it, I noticed that the hall effect sensor in the assembly would trip the relay in the block of fuses under the hood (when the ignition key was turned on) showing the sensor was working, when I moved the sensor close to the bell housing, further away, close again, etc.
That is the ASD relay (auto shutdown relay) which supplies +12v battery
to the fuel injectors, coil and 02 heaters. The PCM controls the low side
of the injectors, coil and heaters. When either sensor goes bad, it is
programmed to shut down the engine. It operates the ASD relay.

in addition to the pouring water over the part scenario to validate the problem, vs the dealer game of big bucks diagnostics, and ultimately move as much of my pile of money to their pile of money as quickly as possible.
The dealer may be able to find it with their scope machine, but yes, it is
going to cost you.

I carry a spare cam sensor in my truck at all times, as that is easy to change
over the hood. Changing the crank sensor is a bit more involved, so I don't
carry a spare one..I would have to call CAA/AAA if it was the cause..but
so far in 14 years, neither sensor has caused any problem..just lucky I guess.

although I suspect I severely over-temp stressed the part so it will likely again begin to fail in the (hopefully not to) near future.
It may or it may not. You really can't predict when these things decide
to fail to heat related stress..but from this experience you will know what
to do next time. :D
 
1 - 6 of 6 Posts
Top