What else to check?!? No matter how/what I try, the thing is a BASTARD to start when hot. I've got a marine battery in the thing now, because the last battery couldn't take the billion or so times the starter had to turn over for the thing to catch.
Compression is above 100 and even on all four cylinders. Spark plug gap is between 25 and 28 thous'.
Head temperature sensor checks out okay, about 2.2k at ambient (70 degrees F), down to 50ohms when fully hot.
The starter turns over no prob, especially with the deep cycle battery, but it takes persistance and dumb luck to get it to spark. New condensor, points, cap, and rotor. The bus idles great when cold (cold start valve works for a few seconds, then to a slightly fast idle, then down to a pretty decent put-put-put staying more or less at 850) Advance is set right exactly where it should be.
The bus runs GREAT until I shut it off for the first time, and then for the next hour or so, it's a total bitch to start, and when it does finally catch, it idles like -CRAP-. Real slow and lumpy. Once it runs again for a little while at highway speed, it idles fine until you turn it off.
Okay, Matt... Check that compression again when hot! Be sure to leave the spark plugs loose from cold engine so you won't rip out the threads when removing them hot. If you coast it down a hill and get it going fast enough it starts and runs, right? It probably idles really rough when hot but not when cold (misunderstood this on yer previous post.) You have a classic dropped valve seat on #3 cylinder - at least that's my bet and my diagnosis thus far! Mine was so bad once that I set the idle speed way up, left it running at gas stops and grocery store stops while on a 1000 mile trip. It made the trip just fine. Ran strong at high rpm; crap at low rpm. The hotter it gets, the more the head crack or otherwise "opening" opens up.
OR - have you checked the fuel rail pressure? There is a fitting along the left side fuel rail to attach a fuel pressure gauge to (the oil pressure gauges I tried just spewed gas - had to get a gasoline one!) You know what the pressure should be - 2 bar at high vacuum, 2.5 bar at low vacuum (or thereabouts!) but check for leakdown. See how long it holds pressure after shutting off. If an injector is leaking (or more) then you might be flooding the engine while shut off. Not a likely suspect, but you say it gets better again after driving a while - that part doesn't fit the popular theme...
Airflow meter vanes stick (never had one stick myself, but have heard of others') Not likely.
I feared the dreaded #3 cylinder myself, especially about 10 days ago when I found the compression at 0 on said cylinder! Repeated testing came up with a flat -0-. hot or cold. But as I said on the other thread, adjusting the lifter seems to fix it, and it now consistantly reads the same compression as the other cylinders.
I'm questioning the injector myself. Every time it won't start hot and finally gets going to a rough idle after a bunch of cursing/praying/playing with the gas pedal (thank goodness for that deep-cycle battery), I start pulling spark plug wires. #4 seems to not make as notable a difference in idle speed as the other three do. I pulled the plug and checked the compression, and it was fine, so I don't think it's a sticky valve. The plug gap was a little wide (close to .30) so I put it at a tight .25, but it didn't seem to make much difference. Could be that the cylinder was flooded at the time due to the wide gap, and maybe it won't do it ever again, but I doubt it. It didn't look wet.
I thought this could be the issue too, because occasionally the fuel pump will whir with the key on and the bus not running, but if I play with the vane I will hear a little clicking out of the relay. I -think- thats a seperate issue, but I'm not really too sure what that's all about in all honesty.
Sounds like I may need a fuel pressure gauge. If I do get one, what should I be looking for? How long should the pressure stay up after I shut 'er down?
on a side note, what is that wire the plugs into a rubber grommet looking thing in front of the distributor all about?
Just to clear this paragraph up, I mean I hear the relay click, but the fuel pump stays on, so I believe the vane is doing it's job. Next time I get a chance and it acts up, I'll check it with the multimeter.
Does it spew black smoke when hard starting? Another thing to try is to just pull the plug off of the cold start injector (on the air plenum, close to the distributor.) I have had that injector start injecting at some very odd times!
The blue wire that goes to that single spade connector in the middle of a weird grommet is your oil pressure sending unit. This is the #1 most likely source of oil dripping from the pushrod tubes! It also gets blown all over everything by cooling air. Approximately 100% of these leak. If anyone has one that isn't currently leaking, it's about to! No, actually there is a high percentage of leaking OP senders. I tried Echlin and one leaked, one didn't. I tried other brands, all had some good, some bad. My luck was about 1 in
3 is good. That "grommet" is very delicate. It's an odd shape, too. BH helpful hint: If you lose oil pressure and the pump won't prime, you can remove the OP sending unit, use a turkey baster and pump some oil (like a half quart) in the hole, re-install the sender, start engine and oil pressure will be back up!
When I bought my fuel pressure gauge, I just bought cheap! You'll need a reading up to around 45 - mine goes up over
100 and when you leave a return line clamped, that pump will deliver over 100psi! You just use a length of FI rated hose and hose clamps to mount it. I don't remember what the specs are, but mine held full pressure over night, as I recall. A leaking injector is going to trickle it off right away.
Not likely that a lifter will pump up and hold the valve open. You can back off the adjustment and run it so it rattles - it should adjust to take out the slack but the slack only.
I haven't yet pulled any of the injector plugs. They look delicate, and I've have no experience with them. Pulling the wire off the cap is real easy, and I've been choosing to stick with what I know. Call me a chicken ;-) Any tips to help me get over my injector plug shyness?
So that little wierd guy is the oil pressure sender eh? Cool. Well, it doesn't appear to leak from the top side, but who knows what lies beneath the odd grommet. Glad to know what it is.
I haven't yet had the chance to check for spark when hot; I need longer arms! I have for sure wondered about that coil though, but the fact that the problem goes away after I drive it for a bit is surely wierd, and makes me think thats not it. I'll have to enlist some help or wire up a starter switch in the engine tin to eliminate it for sure, possibly this weekend.
If you open the oil filler with the engine running, it's opening to the same area as the pushrod tube seals. Hmmm Is there a PCV valve in that crankcase vent circuit? There must be something!
The heat exchangers for a '78 should be no problem. They're multi-year. The '79's are single year and left side California models are extremely rare (Cats!)
While running, wiggle the wires and connectors on the double relay. Should not be related to your problem, but the individual connector pins get loose and sometimes those wires get really brittle, too. I have had the wire that connects to the headtemp sensor break off inside the harness two different times over the years.
Run a timing light up through the rear hatch where you can watch it in the mirror! The wires to the injector plugs do get brittle so they are a bit delicate in that respect. Be sure to pull that coldstart injector plug off and just leave it off for a few days and see if that's the culprit!
Well, there is the mysterious black box with the bail over it, which I understand is the crankcase breather. That's about all I know. Why is the bail on there? Is it supposed to be serviced? I opened it today out of curiosity, and just saw that the walls were coated with black oily stuff, and put it back. Didn't see a PCV valve anywhere, physically or in my studies. But who knows? (certainly not I)
"should be" Haven't found one yet! It'll turn up though, I'm sure.
Tried a bunch of wiggling and rapping in that area, nothing really exciting happened. On that line of thinking, do those resistors go bad? I thought I saw one acting funny intermittently once, but it could've been my meter skills (it was dark out and I was aiming a flashlight at both the meter and the plugs and trying to work the probes.) Wonder if it went to the #4 injector? hmmmm
Thanks so far for sticking with me, next time you're in Maryland the drinks are on me bud!
LOL There's an interesting idea! I dig it, should be doable enough. I need a mirror in the bus anywho.
I'll try out the cold start injector idea... The question is, will it then start after sitting over night in this crazy dc area weather? We'll find out.
Whats the trick to the injector plugs? Just pull? I thought I saw some springy lookin things on there? Do I need to press on anything, or just yank the blue thinger?
you are describing a flooded engine, me thinks. try cranking it with the gas pedal to the floor. maybe you have a stuck open inyector... or a leaky one.
I'm close to that same conclusion. Sometimes opening the throttle plate as you mention does seem to work, but not often enough to rule out dumb luck. I figure I could hook up five light bulbs and run the to the front to check the electrical impulses, but how does one check if an injector is leaking??
take them out and run them in a test bench is one option. another one is to stop it hot, wait 1/2 and hour and then crank it just a tiny bit, then take out the plugs and see if they are really wet...
ruh-roh. i think i have bigger problems. just did a compression check for kicks, and my #3 cylinder is a little on the low side. i hear it whoooooshing too. somethings up in the valve train. what exactly, i don't know. it seems to whoooooosh and give little compression for a few turns, then quiet up and give respectable numbers. sticky valve it seems. fug.
that would also explain why it idles decently after having run for awhile. the real quesiton is, is it just sticky, or is the ever present dropped valve issue getting ready to happen? blah
could also be i'm tired, battery is low, and i'm jumping to conclusions. the starter isn't turning over at the speed it normally does, probably do to me turning the motor over 8000 times in a few hours. charging it now, will play more tomorrow. that whooshing sound scares me though, sounds like an open valve to me.
Ye ole vacuum gauge bounces around a little bit. Nothing looks really all that bad with the rocker covers off. How could i tell if the seat was ready to give, rather then just a sticky valve due to the bus sitting for 5 years? I really want to keep this clunker, but something is whispering in my ear 'SELL, SELL.' Already have an offer...
Others will answer the starting problem, but be kind to your starter and don't crank it for more than a few seconds, then let it cool before cranking again. Otherwise you will be under there real soon now swapping it out.
Good call. I try not to tax it too hard, and the marine battery seems to help as the voltage doesn't significantly drop. I recommend one for all VW owners with a case of the hard hot starts.
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