1978 Bus - Did I Experience "Hot Start"?

[dtrumbo]

Hi everybody!

Just got back from taking the Riviera ('78 stock FI) on her first big road trip. Left Saturday on our 140 mile trip from Seattle to Wenatchee. Pretty hot outside (90's) and two mountain passes between us. The bus did just great. I had my tub of parts and my toolbox on board, but never needed them. We did the reverse trip home this afternoon, again with no problems... until we got home. Pulled in the driveway and shut her down. Unloaded everything and about 45 minutes later I went out to start her up and nothing. Dash lights, dome light, radio, everything else fine, but no start, no crank, nothing. I let it sit for about 15 more minutes and still nothing. After letting it sit for a couple of hours, it started right up. Is this the infamous "hot start" problem? The weird thing is, on the trip over we pulled into the motel (I know, it's a CAMPER, what the hell are we doing in a motel?!?!), shut her down to check in, came back out to park near our room and everything was fine. Could it have been I didn't leave it off long enough while checking in for the "heat soak" to do the voodoo it do to the starter? I've heard of the "hot start" problem and understand what the relay does to correct it, but have never experienced it first-hand. Is this what happened to me?

[IFBwax]

Sounds like it to me! I had the same problem a few years ago.. headed to Seattle and beyond and took a gas stop in Olympia. After we filled up.. dead. But we were able to push start it. Then we drove another two hours to the campground and pulled into the spot. You know me, I had to try it. I killed the motor and turned the key again and it started right up.

I don't think there's an exact science that I've figured out where and when the hot start will hit, but since I got the relay I never had the problem again. Now with the new engine, all new wiring from battery, I still haven't had the problem again.

[spiffy]

Could be. Next time this happens try giving the starter a knock with something substantial, or you could try the wrench start method, OR you could install a hot start relay.

I blamed my continued starting problems on the Bus Depot relay but in reality it was the starter that was going bad. Replaced it and I haven't had a problem since.

[vwlover77]

I used to have the same issue with my '71 Beetle. Replacement of the starter cured it.

[bretski]

Sounds like it could be a hot start issue. I used to have the problem fairly often, kept a long-handled screwdriver handy specifically for this.

About 6 years ago, I installed a hot start relay, and have never had the problem since.

[dtrumbo]

Next time this happens try giving the starter a knock with something substantial...

Tried that, no help. Maybe I didn't whack it hard enough. Ironically, there's a Bosch sticker (still clean enough to read) that says "Do not strike this with a hammer".

Replacement of the starter cured it.

The starter seems to be relatively new as judged by the fact that the stickers (mentioned above) on it are still nice and clean. This doesn't mean the starter isn't bad, you just hope that one that is at least this new-looking wouldn't be failing already.

I installed a hot start relay, and have never had the problem since.

I think I'll do this "just because". I don't subscribe to the shotgun method of fixing things, but it's hard to argue the merits of not running that high solenoid current through your ignition switch.

I have a remote starter switch (fancy long-handled screwdriver) and I should have tried it while it was in failure mode which would have proven the need for the relay. Hopefully, after I install the relay, I won't have the opportunity again.

[dtrumbo]

Thanks for the info Jim! I'll order up the WR-1 and put it in.

Another little trick I've discovered over the years for the Type4 powered bus models is to ditch the heat exchanger flapper valves that have a mushroom shaped diffuser, and replace them with the later model unit that ducts the bleed air down and away... originally via a small pipe or hose

My '78 does have the ducted HE "exhaust" pipes that exit the unused heat out behind the rear wheel.

[RSorak 71Westy]

My bus did the same as yours did once 2 years ago, I cleaned the connections on the little terminal on the starter and it hasn't done it since....

[dtrumbo]

My bus did the same as yours did once 2 years ago, I cleaned the connections on the little terminal on the starter and it hasn't done it since....

I bet this might have been my problem as well. As I was installing my hot-start relay, the connection you referred to was not as snug as I would have liked it. Oh well, as mentioned earlier, having the relay in there isn't a bad thing since it drastically reduces the current passing through the ignition switch. Thanks for the post. It might explain why I had the problem in the first place. I always like to find the smoking gun!

[traveling writer]

I don't mean to hijack the thread, but I have my own "hot start" issue that I could use a hand with!

When I start the bus cold, it cranks hard and fires up straight away. Warm up no problem. Driving no problem. But if I stop the engine, let it cool a bit (a half hour or so), then start again, it still cranks and starts fine, but then idles rough for the first twenty seconds or so. To the point of dying once or twice if I don't goose the gas. What could be causing this?? It's a 77 FI, by the way!

Thanks for any advice!
David

[LiveonJG]

That's a new one tw, I assume if you've been out for a good run, stop for gas and start up everything's fine? Yet after about 1/2 hr rough idle? All that heat that builds up in the bottom end dissipates up (heat rising) as the engine sits. Shot in the dark here but I'd check the connections to your injectors. Heat will cause metal to expand and if you already have a loose connection, the additional heat could make it noticeably worse.

Just a guess.

-John

[dtrumbo]

Here's my guess, and it's just that, a guess. Perhaps your cold-start valve (CSV) is working even when it shouldn't. Is it possible that the CSV is spraying fuel in the plenum during start up even though the engine is already warm? Goosing the throttle would provide a bit more air which would help the situation. The last chapter of the Bentley manual has great troubleshooting steps to test the CSV and the device that controls it, the Thermo-Time switch. Easy enough to test and then you can cross it off the list of potential problems.

[Amskeptic]

Perhaps your cold-start valve (CSV) is working even when it shouldn't.

Hot start problems will not come from an errant cold start spray, that is suggesting that the TTS is actually logical if misguided. Leaky cold start valve is more likely than that, but more likely still is that the fuel rail is losing pressure during heat-soak and allowing the fuel to boil. You can test for 14 psi after ten minutes. If it is 0, you have either a leaking fuel pump check valve or a leaking fuel pressure regulator. . . leaking as in internal bleed-off, not gas on the ground.
Colin

[dtrumbo]

See! Nothing like errant guessing to get Colin to give you the proper method to find your problem. His teaching skills are unmatched! For the thousandth time, thank you for sharing your knowledge!

[Amskeptic]

See! Nothing like errant guessing to get Colin to give you the proper method to find your problem. His teaching skills are unmatched! For the thousandth time, thank you for sharing your knowledge!

Yew are welkem.
So, if you have a residual fuel pressure loss, you will need to clamp the return hose to the tank after warm shut-off and see if the pressure drop is less noticeable. If it is, blame the regulator. If it is not, clamp the hose right after the fuel pump after warm shut-off. If pressure drop is less noticeable, it is the pump's check valve most likely.
Or sumpin
Colin