81 Vanagon starting issue - one try only to get it right

[airkooledchris]

81 Vanagon, stock FI, no EGR/Cat exhaust, AFM slightly fiddled with (though haven't touched it since my itinerant visit)


Like the subject says - I get one shot to start this van lately.
It either fires right up and im gold, or it sounds like its about to fire, doesn't quite start, and now it won't start without a whole lotta crankin.

Im just clueless when it comes to this type of problem, is it flooded, starved, I have no idea. My current system is when it fails, I keep crankin it and then give it light throttle. Do this a few times and if you listen for when it wants to try to start - give it juuuust the right amount of gas, it'll fire - but then you gotta floor it until it comes to life fully and keep giving it a little gas until it's slightly warm or it'll be idling so low that it'll just kill again and then you have to start all over again.

timing is on, points are nearly dead on - not sure where to look next.
I checked my cold start valve late last year and it had checked out ok at that time - which I can check again but id rather get an idea of where to start looking than to just start looking over every damned thing I can find.

I had to start my van earlier after a very short drive to the grocery store - by rolling out of my parking space backwards and popping it in reverse. That doesn't bother me but my wife and child (and dog) use the van when it's nice out and I don't want them to be stuck at a stoplight or something and have to deal with this.

where should I start looking?

(it's been this way for probably 4 months now, but it seems to be getting much worse. used to be I knew the exact moment to give it gas and it would fire every time for me, but im having trouble now timing that perfect moment. )

edited to add: I should have noted this motor is low on compression. perhaps this is just a crappy side effect of continuing to push on with a needing to be rebuilt motor?

[Gypsie]

Just a few ideas....

one is battery condition. If the battery is on the edge it may not be giving enough spark/FI at startup after sitting overnight and directing most of the power to the starter. Then after starting gets an alternator boost while it is warming up....Total longshot though your popstart success is leading (no starter to draw power away from FI/Spark.


I lean more towards the compression/mix interplay. when you say you are giving some gas. This is in effect actually giving more air as you are opening the throttle and allowing more air to mix in. At start up things are a bit rich to begin with (CSV, thermotime switch etc). As well, low compression at warm would likely be really low at cold as seals are less sealed due to heat effect on the metals and oil that has drained down. After things are runnin for a bit the galleys get filled and everything gets slick and compression comes up a bit. I'd be interested to know what your stone cold 'dry' compression readings are. Wait between cylinders to allow the oil to drain back down to get the dry readings.

I also wonder what you find doing the Colin AFM test. Mix at idle, mix at mid and mix at high rpm?

I am going to venture a too rich condition is happening at startup.

Cause?- unclear at this time.

2cents

[vwlover77]

What are the compression readings?

Low compression due to leaky valves can definitely cause cold starting problems.

Any chance you can do a leakdown test to pinpoint whether valves or rings are causing low compression?

[airkooledchris]

The compression test from last summer during my visit with Colin was as such (dry, though not specifically waiting in between for the oil to drain back down.)

#1 66
#2 85
#3 110
#4 120


Battery - I DID remove the hot-start relay that had been installed a long time ago. I was sick of replacing relays when this system would fail, once the relay kept the starter running even after the motor was going and continued even with the van off switched my battery selector to 'none' - then crawled underneath and swapped it out with another. I do have a little 12V gauge sitting on the bench and could toss that in to see if the available voltage seems to factor into things.

I should note however that when it's trying to turn over - it's not slow going by any means, it'll just keep cranking without starting to die down (at least ive never had to go so long that I ran the battery down)


There is a *good* chance that it is just running way the hell too rich. I won an eBay auction the other day (thank you sniping tools!) and got a completely remanufactured AFM for my motor, rebuilt by Python (they sell for over $200+ usually, snagged this one for a reasonable $50)

Assuming that they rebuild them back to stock specs, ill swap it out when it arrives and see if that makes any difference in how it performs. As far as I know my AFM was dialed in pretty well before, but the silver slider screw has since been stripped and it's stuck at it's current setting.


I'll try to get new compression numbers, but will continue to face the truth that this motor will need attention sooner than later. I don't know how long you can run at this low of compression, but im guessing it isn't ALL that long.

[dtrumbo]

My bus does this too. In my case, when my engine is warm I have a very lean condition which I believe is caused by a vacuum leak created by a worn out engine (my number 1 cylinder is 90, the others are 130). To prolong the inevitable, I've richened the mixture when the engine is warm so I don't burn up my exhaust valves. By doing so, my engine is now pig-rich when cold and behaves almost exactly like yours. Remember, when you step on the accelerator you're opening the throttle valve which allows more air into the engine, not more fuel. In my case, this helps the nearly flooded condition I find myself in each time I start the bus when cold. I'm still checking out all of the FI components that could cause this and so far, everything is working properly. I've just richened it up so far to compensate for the warm lean condition, I've sacrificed cold starting performance.

Your scenario sounds similar to mine, of course I can't say for sure. It will be interesting what the different AFM does for you.

[Amskeptic]

81 Vanagon, stock FI,
where should I start looking?
low compression?

Yep.
With a stone cold engine, try to get someone to do the honors up at the key while you check the #86 wire at the double relay for juice. It should light during cranking for a second down in the 40*s and 50*s. If it fdoes not light at all (you get one chance to have test lamp hooked up correctly or you have to wait for at least ten minutes for the thermotime switch to re-establish a ground). If it does not light up at all, you can prime the intake plenum through the brake booster hose connection with a teaspoon's worth of gasoline. Use a funnel and a little bit of small aquarium hose or something, be very sanitary with this step. Put the booster hose back together, make sure it is on securely and that there are no gas spills, and see if it is more apt to fire or less apt to fire.
ColinCompressionDon'tLeaveHomeWithoutIt

[dingo]

or more simply...ditch the thermotimeswitch...and instead power your CSInjector via a toggle switch on the dash. That way, you can give it as much fuel as it may need to overcome its compression issues.


another thing that might help: two batteries hooked up in parrallel..doubles your cranking power