TheSamba.com :: View topic - Hesitation & stalling when hot (was: camping...)

Thu Jul 04, 2013 4:38 pm

My brother was in town with his family this week from Winnipeg so we decided to have a little 'boys getaway' in the bus. That's my bro on the left with his son in the middle and my little guy sampling his first ever roasted marshmallow on the right. Incidentally, this pic was taken almost at 10:00pm and there was still nearly full daylight! Gotta love Canadian summers!

We chose a beautiful spot along the Sheep River in the foothills of the Rocky Mountains. It was 35C above when we left Calgary fully loaded. Unfortunately, the combination of extreme heat, a full load and some steep hills was too much and the engine conked out about an hour into the trip. We had just stopped for about ten minutes at a small town to grab some cold drinks and the first sign of trouble occurred five minutes outside of town. It started with some hesitation and loss of power which rapidly deteriorated until it flat out stalled with a couple of pops. I figured the engine was heat soaked from the short stop so we let it cool down for about half an hour while I did some rudimentary checks of plug wires, vacuum lines, fuel lines, etc. and all was in order. The oil dip stick was hot but not so hot that I couldn't hold it. Checked the oil and it was fine. So at this point I suspected either a bad coil (new 1000 miles ago) or a bad/loose TSII (new 700 miles ago). I didn't have my spare parts or a multimeter with me so I had no way of knowing. After the cool down, it started up and we were on our way again, running like a top. 10 minutes later though it reoccurred. Waited half an hour and off we went, again running fine. By this point we were just five minutes from the campground and we were able to limp in before it happened again. The forecast for our return trip was a much more reasonable 22C so I figured we wouldn't see a resurfacing of the problem. However, the hesitation came back about an hour into the drive. Very intermittently though, and it never stalled. Just bucked a few times under heavy load so I would down shift to 3rd even on slight grades and it seemed to like that. I'm going to test the TSII and the coil tonight but I thought I'd ask if there were any other suggestions as to what I should check. Everything on this engine is new as of 1000 miles ago and all is tuned to factory specs. The tank was cleaned and new lines/filter were installed as well. The one question I have when testing the coil is, will a cold coil show the same resistance as a hot one? ie, should I go for a drive before I test it?

Thu Jul 04, 2013 4:52 pm

Hey Ben. Hmmm, sounds like it might be running too lean as it gets hot. Had a similar issue with Mrs Westfab's bus. That required addressing all potential vacuum leaks, etc, replacing a few bits and pieces, including on the EGR set-up, then the final step was re-calibrating the AFM. I did that myself, and had to tweak it a few times, but I have never been a bus that runs better. Age also factors into these things running lean.

IMHO, this is a hot/ cold running issue, and you need to approach it from that angle.

FWIW, we climbed some real big SOB hills with a full load going to Tofino, and apart from one spot where I could tell that the engine was just beginning to protest, all was good. That was my bus, not Mrs Westfab's, but I also re-calibrated the AFM on that one too.

How's the fuel filter?

Thu Jul 04, 2013 5:36 pm

Thanks Dan. I thought about a lean condition but I haven't had this problem in the past and I've gone up some major climbs with the bus loaded as well. That and the fact that even in the 35C temps, the engine itself didn't feel abnormally hot leads me away from a fuel/mixture issue. I haven't actually checked the fuel filter yet but as I mentioned, everything in the fuel system is new including the filler hoses. The hesitation and bucking was an abrupt cut out rather than a sputtering. I'll check the ignition components and will report back. Any insight as to whether a hot coil will test the same as a cold coil?

Thu Jul 04, 2013 6:31 pm

check your FI ground.. probably not it but always a good place to start :D

Thu Jul 04, 2013 7:11 pm

AB westy nut wrote: Any insight as to whether a hot coil will test the same as a cold coil?

I tested mine dead cold in winter and it fell within specs.

Thu Jul 04, 2013 7:46 pm

Try grounding the TSII connection where it plugs into the wiring harness to a known good ground.

Fri Jul 05, 2013 8:41 am

Well I tested the TSII and it was within spec. Then I tested the coil and the primary resistance between terminal 15 and terminal 1 was only 2.7 Ohms. The secondary resistance measured 8350 Ohms. Could the low primary resistance cause the hesitation/loss of power/stalling under load when hot?

By the way, the FI grounds are all clean and tight.

Fri Jul 05, 2013 8:10 pm

Just wanted to pipe in that the bucking and hesitation issues I had last year was seemingly caused by a lean condition. This was cleared up by a series of AFM adjustments Performed by Amskeptic last September.

The bus never ran better...until today. The bucking and hesitation under load in 1st & 2nd returned today. Today was also the hottest day we have had so far this summer.

Also, my alternator light started glowing faintly.

I am at a loss on where to start trying to tackle this problem again.

I will be watching this thread for some clues hopefully.

Fri Jul 05, 2013 8:48 pm

This is also the symptom of a clogged sock filter in the tank. It can run you lean.....but the real show stopper comes when the sock filter clogs and the pump cavitates. Letting it sit still helps...but not because of a cooling cycle but because the sediment in the tank sttles out allowing fuel flow again. Check the feed to your main filter. Ray

Fri Jul 05, 2013 10:50 pm

Or a clogged fuel filter or Pump starting to fail since, the 76 does NOT
have a 'Sock type filter in the tank.

Also, with your Alt light flickering... it could be a voltage problem other than the fuel pump drawing excessive amperage.

Sat Jul 06, 2013 6:47 am

Learn something new everyday. Glad they eventually got rid of the worthless sock filter....worthless and redundent...as the original factory D and L jet filters had a packed lint pre-filter built in them (most don't anymore).

Yes...good catch. It could be incomplete charging. Once the battery gets too low....it conks out....and runs porrly while its heading that direction. Ray

Sat Jul 06, 2013 8:57 am

raygreenwood wrote: Learn something new everyday. Glad they eventually got rid of the worthless sock filter....worthless and redundent...as the original factory D and L jet filters had a packed lint pre-filter built in them (most don't anymore).

Yes...good catch. It could be incomplete charging. Once the battery gets too low....it conks out....and runs porrly while its heading that direction. Ray

I won't hi-jack this thread anymore after this reply.

- Battery with ignition off = 13.6 V
- Start up at idle, alternator light steady on (it has always done this at start up until I step on the accelerator a little) = 11.66 V
- Rev engine and let settle down to normal idle. Alternator light glows at about 1/2 intensity = 14.6 V
- Rev engine and hold at about 2,000 RPM. Alternator light at about 1/4 intensity = 14.0V

Thanks, I am a bit tired of chasing this persistent, intermittent problem.

And now I turn the thread back over to our original sponsor....

Sat Jul 06, 2013 9:24 am

Sounds to me like a classic symptom of the voltage regulator. I'm not all that up to speed on how the alternator in the bus works with its remote VR but I know that on alternators with an integrated VR, the brushes get worn down producing an effect exactly as you describe. Maybe there's an equivalent thing going on with your bus?

Also, have you checked the primary and secondary resistance of your coil? From what I've read, the coil is susceptible to heat. This can cause a weak spark and subsequent hesitation and bucking.

Sat Jul 06, 2013 9:41 am

I am starting with cleaning all grounds. Even though I have done this numerous times before while chasing this issue.

I think I have a new spare VR and will try it.

Coil resistance is 4.0 Ohms

Thanks.

Sat Jul 06, 2013 9:51 am

Put an ohm meter across the '15' and '1' terminals of the coil to measure primary resistance. It should be within the 3.0 to 4.5 Ohm range. Put the meter across the tower and the '15' to measure secondary resistance. I believe this should be in the 6k to 10k Ohm range.

My primary resistance is low at 2.7 Ohms and I'm trying to find out if that's enough to be causing the hesitation.

Sat Jul 06, 2013 10:01 am

AB westy nut wrote: Put an ohm meter across the '15' and '1' terminals of the coil to measure primary resistance. It should be within the 3.0 to 4.5 Ohm range. Put the meter across the tower and the '15' to measure secondary resistance. I believe this should be in the 6k to 10k Ohm range.

My primary resistance is low at 2.7 Ohms and I'm trying to find out if that's enough to be causing the hesitation.

Thanks for the instructions. Not sure if I am doing it correctly.

Primary is 4.0 Ohms

Secondary is infinite?

Sat Jul 06, 2013 11:18 am

Do you have your multi meter set to the right range? It should be set to 20k ohms.

Sat Jul 06, 2013 11:31 am

AB westy nut wrote: Do you have your multi meter set to the right range? It should be set to 20k ohms.

Oops, no. :oops:

Secondary resistance is 8.6K.

Thanks. I am not really too proficient mechanically, but far worse electrically!

Sat Jul 06, 2013 3:30 pm

Ok, back to my original problem. I ran a few more checks:

1. Coil tested good after I disconnected ALL of the leads from it. :oops:
2. EEC tested and held vacuum.
3. Micro switch on throttle body doesn't pass the test light test as per Bentley but it does open and close properly when tested for continuity. I also get voltage to it when I should with the ignition on. So I'm not sure why the test light doesn't light up.
4. I did the 'quick light pumps of the brakes at warm idle' test and found very little to no discernible change in RPMs.
5. Pulled the #3 plug (engine cold) and it's a tan colour, but to me it looks a bit lean. Here's a couple of pics. What say the experts?

The plugs, like everything else, have about 1000 miles of mixed diving (mostly freeway) on them.

Sun Jul 07, 2013 3:11 am

Looks a little lean to me