1997 Safari engine shut down at highway speed

[rides2fix]

After about 5 minutes of driving, with about 1 minute at 55 -60 MPH the 3.4L engine died as if I turned the ignition off. After coasting to a stop it started right up as if nothing was ever wrong. I drove for about another mile or so when it did the same thing again. This time I tried to restart while coasting in neutral and the engine started on the second try. I then drove another 2 - 3 miles to my destination without any further problems.

I have just replaced the intake manifold gasket due to a coolant leak and then had to take the upper intake apart again because the fuel pressure regulator failed. Since I have around 150,000 mile on the engine, I decided to change the whole fuel meter body. The engine seemed to run like new after this and for 4 days prior to the loss of power described above.

I have had problems for years with some sputtering during wet or damp weather and although we had significant rain over the 4 days after my latest repairs, there was no indication the damp weather had any affect on the engine now. When the engine cut off going down the highway, there was no sputtering or anything, just a clean shut down -- all I noticed was unexpected decleration.

There were no codes set and none pending either. I have not driven it since, but have run it in the driveway a couple of times that total over an hour of run time and the engine hasn't faltered once. I have jiggled all of the wires and connectors at the VCM, sensors, coil, and ignition module; all with no affect on the engine.

Although it was not hot the night the engine died, I suspect the ignition module and if it wan't so expensive, I would just replace it. Unfortunately, my plans to just drive until it fails again are delayed becuase of a radiator leak that just popped up today while I was hooking up equipment to monitor the coil primary.

Does anyone have any ideas on how to track down this type of intermittent problem?

My apologies for the long post.

Thanks,

rides2fix

[dewaynep]

Sounds like the crankshaft sensor is going. Check for spark when it shuts down and won't restart.

[Leeann94astro]

Pull the ignition control module and take it to an auto parts store and have it tested. Have it tested several times, not just once (they tend to fail when they get hot).

[old_master]

If the coil wire, (from the ignition coil to the distributor) is not routed correctly, the insulation can rub through on the transmission dipstick tube and short out secondary voltage to the distributor.

If the vent screen in the bottom of the distributor is clogged, condensation can form on the underside of the distributor cap and cause symptoms like you're describing also. A GM TSB instructs the technician to completely remove the screen. Probably be a good idea to install an AC Delco cap and rotor while you're in there.

....Just a couple of things to check

[rides2fix]

Originally Posted by dewaynep

Sounds like the crankshaft sensor is going. Check for spark when it shuts down and won't restart.

I just got the radiator back in tonight and drove about 15 miles with both highway and stop and go driving without any problems. I am set up to check for spark should it fail again. Would an intermittent crank sensor cause a code to be stored?

Originally Posted by Leeann94astro

Pull the ignition control module...have it tested several times, not just once (they tend to fail when they get hot).

Although it was pretty cool out when the engined failed (my experience has been more ICM failure on hot summer days), this is my primary suspect until I prove otherwise. Do the testers they use stress it to cause weak ones to fail.

Originally Posted by old_master

If the coil wire...the insulation can rub through on the transmission dipstick tube...

Pretty good shape there; corrugated tubing around the coil wire.

Originally Posted by old_master

If the vent screen in the bottom of the distributor is clogged...A GM TSB instructs the technician to completely remove the screen...

I forgot to mention that I replaced the cap & rotor when I put the intake back on - used Echlin from NAPA, but am willing to go for Delco if that may reslove the problem. A copy of the TSB was included and I recall seeing one a few years ago when I replaced these. The problem is I don't see any vents on the bottom of the distributor - even considered drilling some holes, but haven't. Any thoughts on that?

I really appreciate all the feed back from everyone. I have 6 people going in different directions in 5 vehicles every day and having this van out of service is a major headache. I could probably drive it and baby it along, but no one else can drive my manual trans truck. I plan to drive it for the next couple of days, but from what I have seen in other posts this may be something that will take some time to track down. Plus, if it is a heat issue, having the engine cover off so I can quickly troubleshoot may not be a good thing.

Thanks again.
rides2fix

[old_master]

Originally Posted by rides2fix

....Would an intermittent crank sensor cause a code to be stored?

YES, absolutely it would. Any circuit that the ODBII monitors will set a DTC if it fails, even momentarily.

Originally Posted by rides2fix

Do the testers they use stress it to cause weak ones to fail.

NO, they simply test for switching, no stress test or heat involved.

Originally Posted by rides2fix

A copy of the TSB was included and I recall seeing one a few years ago when I replaced these. The problem is I don't see any vents on the bottom of the distributor - even considered drilling some holes, but haven't. Any thoughts on that?

From the underside of the distributor housing, it looks like part of the casting. If you remove the cap you can see the screen, it's about 1/4" in diameter. I usually just run a drill bit down through it...all gone!

You might want to connect a fuel pressure gauge to the service port and watch it when the engine quits. GM doesn't publish any engine running fuel pressure specs for this engine but, it's usually around 57psi while cruising, lower when decellerating, higher when accelerating. The poppet valves need right around 40psi to squirt fuel and when it drops below that, it can act very much like an electrical failure, very "digital". Key on, engine off, fuel pump running, pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off.

[rides2fix]

Originally Posted by old_master

From the underside of the distributor housing, it looks like part of the casting. If you remove the cap you can see the screen, it's about 1/4" in diameter. I usually just run a drill bit down through it...all gone!.

I thought I looked it over pretty good, but will definately go back and take another look.

Originally Posted by old_master

You might want to connect a fuel pressure gauge to the service port and watch it when the engine quits. GM doesn't publish any engine running fuel pressure specs for this engine but, it's usually around 57psi while cruising, lower when decellerating, higher when accelerating. The poppet valves need right around 40psi to squirt fuel and when it drops below that, it can act very much like an electrical failure, very "digital". Key on, engine off, fuel pump running, pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off.

I have been running it with a gauge hooked up and the pressures are right on target with your values. I also have a voltmeter semi-permanently attached to the primary of the coil so I can compare the base line values captured under various operating conditions to when (if) it fails again. My thought is to work back through the ICM to the VCM if no voltage at the coil primary at time of failure -- assuming the fuel pressure is good at the time. What is the probability of an intermittent problem with the fuel pump on this vehicle? Also, I changed the fuel filter before installing the new spider assembly.

It made the round trip to work today without incident. Went out lunch time and ran it for awhile too and it hasn't missed a beat. Sure hard to fix when its working.

Thanks again!

[old_master]

The connector at the fuel pump module is a known issue. It gets hot from high resistance and then melts the connector. Worst case senario... no voltage gets to the fuel pump. In the early stages it can be intermittent.

[rides2fix]

Originally Posted by old_master

The connector at the fuel pump module is a known issue. It gets hot from high resistance and then melts the connector. Worst case senario... no voltage gets to the fuel pump. In the early stages it can be intermittent.

It finally died again today on the way home from work (of course I was merging at the time ). Anyway, it appears I am heading towards the fuel pump or its electrical connector. As soon as it died, the fuel pressure was 0. This time the engine did not start up right away - took about 5 minutes and several atempts at starting. The fuel pump did not come on when the ignition switch was turned on or via the oil pressure switch ckt while the engine was cranking.

old_master, if the connector is OK do you think it safe to say replace the fuel pump or should I check anything else. I saw a reference to applying a fused 12v supply to the pump's test terminal - is that located in the underhood fuse-relay center and attached to the NC term of the fuel pump relay? If worthwhile, I could possibly be ready to check this when it fails again.

Many thanks for your help.

[old_master]

I can't recall for certain if there is a fuel pump prime wire, (red wire with eylet) near the fuse box or not on your '97. It would be a good idea to at least check the fuel pump relay in the underhood fuse panel. When you first turn the key to the run position, it should click then after 2 seconds click again. The next test would be to test for battery voltage at the fuel pump connector, grey wire, should show battery voltage for 2 seconds when the key is turned on. Then test the black wires, in the fuel pump harness connector, for resistance to ground, should be less than 5 ohms. If you have battery voltage and resistance checks good, the fuel pump needs replacement. Keep us posted.

[rides2fix]

Pulled the gas tank out tonight and found the culprit. The fuel pump electrical connector at the top inside the tank overheated and the terminals were barely making connection. old_master, you hit that one on the head as far as possibly showing up as an intermittent problem before going out completely.

Here is a link to a picture of the conncetor and pigtail assembly.



Thanks again for the assist.