Mysterious missing

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jolotter
Diesel Freak
Posts: 114
Joined: Thu Sep 20, 2007 11:05 am
Location: Toronto, Ontario

Mysterious missing

Post by jolotter »

I've put about 10,000 mi. on my 1.6TD since a full rebuild. I have a miss and stall issue that I shall describe.

This occurs irregularly but only when the engine is stone cold.

Pull the cold start cable, glow for about 7 seconds, crank the starter and the engine fires right up, oil pressure light goes out. Idle for about a minute, then pull away in 1st. SOMETIMES, as I accelerate, the engine will start to miss then stall.

If I crank the starter right away, the engine spins, but fast like it has no compression. Then I wait about 3-5 minutes and will start up again but rough like the lifters aren't pumped up and it's only running on 3 cylinders but then it smoothes out as I drive away.

What's up with that? Cheap lifters?

Johann
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
ctange
Cetane Booster
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Location: Copenhagen, Denmark

Post by ctange »

Have you checked det dieselfilter?

There are mecanical lifters on a vanagon.
1989 1.6TD Diesel vanagon
1987 1.6D Golf Aut. Gear
jolotter
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Post by jolotter »

The filter has 10000 mi. on it. Should be fine.

The lifters are hydraulic. from a 1990 jetta.
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
Fatmobile
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Post by Fatmobile »

I'm thinking air in the fuel.
Do you have clear fuel lines?
Have you looked for air in the lines to and from the pump?
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
jolotter
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Joined: Thu Sep 20, 2007 11:05 am
Location: Toronto, Ontario

Post by jolotter »

I looked for air in the fuel lines today, and with the exception of a small bubble at the high point of the return there was none. I think that one's left over from when the fuel feed at the filter was not tight and I put a hose clamp on it rather than the spring clip that was there previously.

I started the engine and watched as I blipped it a few times. No air anywhere, but it didn't stall either. I think I'll replace those lines anyway as they've been on and off afew times and are getting hard. (only 2 years)

BUT, I don't think that's the issue. Like I mentioned before, when it stalls it's like there's no compression and the engine spins with no resistance. If I pull the fuel cutoff wire and crank it (when it's been running normally, ie. hasn't stalled), it turns over with that cyclical compression/no compression sound.

Next time it stalls I'll jump out and look for air, to be sure.
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
jolotter
Diesel Freak
Posts: 114
Joined: Thu Sep 20, 2007 11:05 am
Location: Toronto, Ontario

Post by jolotter »

I've had a couple of stall incidents lately. The first was like the others: cold start, 30 second warmup, pull away gently and stall before my first gear change. I jumped out to check for air and the lines were full. Then about 2 to 3 minutes of "no compression" before it'll run again.

The next was a similar start but I revved it at the curb and it stopped dead. Again, no air in the lines. This time it started after about 30 seconds waiting.

I think it must be an oil pressure issue like maybe the lifters are collapsing. usually after it happens it will start but missing on at least one cylinder for about 30 seconds. I also get a huge cloud of white smoke when it starts again, leading me further from fuel starvation diagnosis.

Johann
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
Josh
Turbo Charger
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Joined: Wed Oct 09, 2002 7:30 pm
Location: Algonquin, IL

Post by Josh »

It's really strange as if anything, the oil pressure to the head should be higher when the oil is cold and stiff, correct? Theoretically, I'd think the lifters would have a harder time if the oil was hotter and therefore thinner. The fact that you've got a somewhat opposite condition is baffling. (I'm assuming it runs well once warmed up, and your stall issues are interspersed with periods of functionality)

I've no experience with the hydro heads, tho. Pure speculation.
-'79 rabbit, getting parted out
-'82 quantum wagon, gutting.
-'84 rehabbed quantum TD sedan, southern rustless beauty for sale
-'82 cherry Westy from AZ
-more all the time; are they breeding?
rsxsr

Post by rsxsr »

If the oil pressure is too high after start up, the lifters can overpower the valve springs holding the valves open. Hence you zero compression sound when cranking. It is possible the oil pressure relief valve is stuck in the oil pump housing causing this. I'd recommend an external oil pressure gauge. The other option is to drop the pan and check the pump. Regards.
jolotter
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Post by jolotter »

Thanks rsxr,

Oil pressure gauge is on the list. I will check the valve on the pump when I put the van away for the winter in a few weeks.

If the valves were staying open wouldn't I get piston to valve contact? :(
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
rsxsr

Post by rsxsr »

They only need to be held off the seat to have zero compression. My suggestion is a stretch, but we did have cars under warranty that had a problem with the relief valve in the pump. A cold diesel will see 100 pounds oil pressure easy. When VW introduced hydraulic lifters, they also updated the oil pump. It had taller gears rated for more volume and lower pressure. Did you account for the oil pump when you upgraded to hydraulic lifters? I don't know anything about the 1.9 MTD. The 1.6 diesel had an oil pump specific to the diesels. The pump drive shaft was different to the gas models and was not a drop in replacement. Just something to consider. mark
Josh
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Post by Josh »

If you swapped in a motor from a 90 jetta, that stock oil pump shouldn't be a source of the trouble. But if when everything was rebuilt and the smaller older designed lower-volume pump (still available and common) was put in by mistake, I suppose it could be the culprit.

I don't believe there was a stock 1.9 "MTD", assuming you're referring to a mechanical head with the letter M, rsxsr.

-Josh

ps. The newer diesel oil pumps for the hydro heads are backwards compatible with the older engines.
-'79 rabbit, getting parted out
-'82 quantum wagon, gutting.
-'84 rehabbed quantum TD sedan, southern rustless beauty for sale
-'82 cherry Westy from AZ
-more all the time; are they breeding?
rsxsr

Post by rsxsr »

Josh wrote:I don't believe there was a stock 1.9 "MTD", assuming you're referring to a mechanical head with the letter M, rsxsr.

-Josh

ps. The newer diesel oil pumps for the hydro heads are backwards compatible with the older engines.
I was using the M to designate the difference between a "Fly By Wire" 1.9 TDI that I have transplanted into my Vanagon and a 1.9 TD with a Mechanical Injection Pump. Sound engines don't have good compression one minute and none the next. My suggestion is based on my experience with engines that had his symptom. It would be rare, but would explain how the compression could be there and gone and back again.
libbybapa
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Post by libbybapa »

Many folks just fit the vanagon pickup tube onto the newer pumps. This is not correct and can lead to excessive oil pressure at cold start causing the lifters to hold the valves open as mentioned. This is not exactly common, but not uncommon either among the vanagon conversion crowd. If the stock diesel vanagon oil pump pickup tube was used with the larger geared pump, then that could be your problem as it has a pressure relief valve that is sized for the 30 mm gears which is too small to relive the cold pressure of the 36mm gears. The easy solution is to get the correct 36 mm vanagon turbo-diesel pump which is still available for $150 or so from various vendors.
jolotter
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Post by jolotter »

Michael,
that would explain why when I blipped the "throttle" and it stalled I could start it again after a relatively short time, whereas when I drove off and it stalled and the momentum of the vehicle kept the engine turning over and pumping up the lifters more, it took a few minutes to relieve the pressure before i could start it.
I remember looking at the two pumps and thinking, taller gears = more oil flow = better. I'll dig out that other pump.

I guess the short term solution is to warm it up a little longer.
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
jolotter
Diesel Freak
Posts: 114
Joined: Thu Sep 20, 2007 11:05 am
Location: Toronto, Ontario

Post by jolotter »

Well with the daytime temperature maxing out around 10 deg C, the "short term solution" is not cutting it any more. today it took four times of start-stall-wait before it would idle long enough to warm up. Since this snuck up on me I was puzzled until Libbybapa explained his theory. It fits with colder temps bringing higher startup oil pressure.

It is encouraging indication that the oil pressure is rising since my full rebuild as the parts wear together. I had none of this last fall after 4 months on the engine.

Johann
83.5 Westy 1.6 TD
93 1.9TD engine in the shed
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