Strange, intermittent cut out

[DougB]

Hello all,

Posting a new question just to make sure that the full situation comes through.

The basics:
'75 Westy with Camper Special (stock FI), 45K miles on the engine, 196K on the vehicle
Good charge from alternator (14V when running)
29-35 PSI fuel pressure when running (have a DD fuel pressure gauge)
Good oil pressure and oil temps
No recent work to the engine that would have triggered an issue
No high CHT issues (pretty much runs between 320 and 390 degrees when cruising at highway speeds)

The situation:
Without rhyme, reason or pattern, I'm getting an intermittent cut out of the engine's power. It usually happens when I'm running at speed (engine at 2500-3200 RPMs but fluttering the throttle doesn't instantly solve the problem, so I don't think it's throttle position-related).

The cut out is usually just momentary, but in the past few days it's been lasting for a few seconds, and today it stranded me at the side of the road for about 20 minutes (only did that once before, 2 years ago). During that time it just wouldn't start, though the starter itself was working fine. It doesn't seem to happen based on any particular level of engine/CHT heat - the time 2 years ago we'd been cruising for hours in the summer, today I just ran out to grab lunch on a 50 degree afternoon.

That time a while ago I replaced the TS2 at the side of the road and by the time I was done the engine started...but this time I replaced the TS2 again and it had no effect...so I'm wondering if the engine just need to sit for a bit.

While stranded I checked connections and felt around...the coil was not hot at all, no undone plugs. Perhaps this was from me repeatedly trying to start it, but the battery ground strap was warm, but definitely not hot.

For all the cranking, one thing I did not notice was any fuel smell...maybe FI knows not to flood the cylinders and make the puffs from the muffler smell like unburned gas...but my FI pressure sensor is just before the cold start valve so it seems that the rail is pressurized.

While unstartable the car had all the typical electrical power I'd have expected. Disconnecting and reconnecting various FI connectors in the engine bay (attempting to cure any momentarily missing contact) had no effect.

This engine typically purrs like a kitten and is a strong highway runner for minutes or hours. I do have at my disposal spares for most or all of the FI components, and most are actually in the car at all times.

Any suggestions for what I might try the next time this happens? Would the key ignition switch ever do this (engine cut out but with all electrical power still there) if it was wearing out? Just wondering as I've not checked that before.

Many, many thanks in advance,

- Doug
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'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife

[Tram]

Is your fuel pump louder than normal? Is it HOT when the car stalls?

Carry a timing light and a fuel pressure gauge for when this happens next and diagnose it. Logic tells me it's a fuel issue because it doesn't smell of gas when you try to start it but this should be verified first.

One thing I started seeing a lot of failures on towards the end of my repair shop days on FI Buses was the little "eye" that grounds the wire at the multi relay. Either the screw would be loose or it needed a new "eye" connector installed at that position because, even though it was visibly OK, there was a loss of connectivity between the eye connector and the wire in it.
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[airschooled]

Hi Doug,

An ignition switch issue would cut other electronics too, but you can rule it out by powering the coil straight off the battery when troubleshooting.

Have you checked for spark during the no-start events? Take the hi-tension lead off the distributor cap (center) and hold it a cm from a clean ground while the engine cranks over. We want to see strong and consistent. (I don't care about color because ozone in the air affects spark color far more than ignition system components.)

On a warmed up engine, you can also bypass the TS2 by grounding the wire from the harness. I have witnessed one bad TS2 out of the box in my lifetime, so it's something I assume now………

When not starting, could you prod the flap in the AFM with the key on, so we know the double relay is triggering the fuel pump?

Robbie
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[Xevin]

Doug you have a shit ton more knowledge then me. However I experienced similar issue last year. Turned out to be the distributor cap contacts had some carbon build up. Sanded clean and problem solved. Then replaced cap at the next FLAPS. Not saying this is it. But quick and simple to check. Good luck
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[raygreenwood]

[DougB]

Thanks for all the suggestions so far!

I'm definitely onboard with tracking down ground issues...my mind was going there as well, and the battery ground strap may be the original for the car, so that seems like an easy place to start. Then I'll move to the other engine area grounds like the "eye" mentioned above.

As for the fuel system, I'm really diligent about replacing the fuel filter cartridge (I use a Canton fuel filter with replaceable elements) but will check it and the pump action, too. I didn't notice anything being louder than usual in that area, though.

Keep the suggestions coming if you have 'em...thanks again!

- Doug
_________________
'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife

[SGKent]

what kind of ignition system are you using? Stock or electronic?

Is the fuel pressure gauge upfront where you can see it when the engine cuts out? If so then what is it showing when this happens?
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[DougB]

Stock ignition coil setup but with a Mallory Unilite distributor. No points in there, and the cap & rotor are pretty recent.

One thing I will say is that even before the Camper Special switch over, the old engine did something like this too (though only the instantaneous power loss/miss, and it tended to go along with a bump in the road in a way that the current power loss does not). All the FI components and harness on this engine are from my old one - I shipped that to Jake so he could use all the components. So there's a chance that whatever is causing the issue was actually an issue even prior to the new engine.
_________________
'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife

[DougB]

Yes, the fuel pressure gauge is up front and it still read good pressure (35 psi) when the bus was stranded...but I didn't think about it in time to see what it's doing when I'm moving but in a powerless condition (where the speed is just dragging the unrespsonsive engine).

I have a PLX Devices AFR meter on this engine, too, and when this powerless condition occurs the gauge just reads "AIR" though that could either be due to no hot exhaust there for the O sensor to detect.

This is probably way too much info...
_________________
'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife

[aeromech]

I think it could be your ignition switch
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[SGKent]

Like others, I'd be inclined to think it is the ignition switch or the connector at the bottom of the steering column BUT with an electronic ignition you can't know that it isn't involved unless you check for voltage at #15 on the coil and also put a timing light on #1, to see if you get a flash about the right time when you crank it over at the ignition switch. If there is no voltage then it is up front. If you have voltage but no flash then it is somewhere around the Mallory unit or the unit itself. One thing to consider is that the ignition switch has a separate set of contacts when in the start position. If it fires up in start but dies when you let go of the key then it would be the switch. The connector at the base having a loose wire would affect it both start and run.

It could also be the wire going from the coil to the ECU is broken internally at the spade lug where it goes onto the coil, especially if it is the original wire. That would cause a bad signal to the ECU so you would get no firing of the injectors. Putting a noid light on one injector when it won't start would let you see if the injectors are firing. If they are and you have fuel pressure then it has to be power or ignition related.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Wildthings]

I would look for a pin that has been pushed back out of the plug for the AFM or ECU. They can make decent enough contact to work for a long time and then suddenly from heat and/or vibration the pin moves a little and contact is lost and the engine dies.

[DougB]

When I left work today I started the van and it idles well, but stumbled once while idling. Then I decided to use my jumper cables to make a better ground from the battery to the frame (while using a bungie to keep the rest of the cable away from anything spinning or sensitive). Van ran great the entire way home with no additional stumbles, but I'm not going to call it solved by any means as it's given me trouble-free periods before.

I'll check all of the suggestions if it craps out on me again, but in the meantime maybe I'll try wiggling the key a bit when it's running to see if that causes the problem (Colin always warned me about having too heavy of a keychain so I only use a single key, but who knows what the original owner before me did).

Thanks again!

- Doug
_________________
'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife

[SGKent]

if things that pull more power like lights etc., cause it to act up more one might suspect the ignition also. A bad battery ground or positive can toast the alternator so by all means get a good ground on it.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[SamboSamba22]

My two cents are on clearance, so take them for a penny. I experienced a similar issue with my dual carb setup in my 74 Westy. All of this would happen randomly under load going down the highway, sometimes it'd sputter and pass, others I'd have to pull over. Drained tank and installed the new screen tank filter ( I never installed it after removing the old one) and thousand miles plus I have yet to experience the same issue.
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[Mopar2u426]

Remember that with heat...come higher resistance values...I would suspect that the ignition is breaking down under a warm condition..do you have points or a magnetic pick up (Ignitor) ignition? I have seen the distributors short out...If this happens again, quickly check to see if you have spark..if not..look to the distributor or it's components.

[Wildthings]

I have my battery grounded directly to one of the bolts on the fan shroud. Seems like a much better way to me than running the ground to the frame and then through the tranny nose cone ground strap.

[DougB]

Good call...I picked up a few different ground cables in addition to a new one from the battery, so perhaps I'll go around and replace the stock ones as well as add one or two.

Most annoying thing about the super-infrequent (and possibly stranding) nature of intermittent issues is that you're never immediately sure if/how well the "fix" solved the problem :-/ Driving these things can't all be fun and games, I guess

Thanks again, all!

- Doug
_________________
'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife

[lil-jinx]

If grounding the eng directly to the battery you will still need a body ground to the battery.
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[DougB]

Yes, definitely! Not looking to replace one method with another as much as creating redundant connections.
_________________
'75 Campmobile (tin-top to SpaceRoof)
'73 Fastback
'52 BMW R67/2
'41 Zundapp KS600
'55 Puch SGS250
A very, very understanding wife