77 FI Bus Fuel Leak at Heads

[Gypsie]

????

Towed home? So you were driving, stopped, and when you went to start it up again it wouldn't?

Would a swap of plug wires make the spark hit at the wrong time and therefore leave a bunch of unburned fuel in the cylinder needing an escape route? P'raps you've been pranked.

The amount of fuel and locations just 'feel' like cylinder head compression venting.
Have you located extra fuel topside?

How long did you try to start it before smelling gas? Have you looked down into the plug holes to see if there is fuel in the cylinder. If you can't see in there stick a long stick to the bottom of the cylinder and see if there is fuel pooled (I'm thinking something like a sishkabob skewer dipstick thingy...)


Perplexed....

[EZ Gruv]

So you were driving, stopped, and when you went to start it up again it wouldn't?

Precisely.

Would a swap of plug wires make the spark hit at the wrong time and therefore leave a bunch of unburned fuel in the cylinder needing an escape route? P'raps you've been pranked

Nope. When I arrived at my destination, I shut off the bus, went around to the sliding door, put 10 boxes in, closed the sliding door, and got back in the drivers seat and attempted to start the bus. No one else was in sight. This all happened within 3 minutes.

Have you located extra fuel topside?

There is no fuel on the top of the engine, if that is what you are asking.

How long did you try to start it before smelling gas? Have you looked down into the plug holes to see if there is fuel in the cylinder. If you can't see in there stick a long stick to the bottom of the cylinder and see if there is fuel pooled

I let the bus sit for a few minutes before trying to start it again, but after I spent 15 seconds cranking it I smelled gas. As far as fuel in the cylinder, when I pulled the spark plugs, they were wet, but I don't know if there is a pool of fuel down there.

[bretski]

Did you get a chance to do the fuel-pressure test?

[EZ Gruv]

Did you get a chance to do the fuel-pressure test?

Gauge is in the mail right now, could be here tomorrow.

[vwlover77]

In the meantime, Turn your ignition on, then move the AFM wiper away from its rest position. This will turn on the fuel pump. What do you hear?

Under normal circumstances, you'll hear the happy quiet hum of the pump and the fuel flowing through the fuel lines, through the pressure regulator, and back into the tank from the return line. Maybe even some gurgle from the fuel flowing back into the tank.

Try it and let us know.....

[Amskeptic]

I don't think the cold start injector could spray enough fuel to flood the engine to the extent we're seeing here.

It could . . . Your average fuel injector pulse is measured in the thousandths to hundredths of a second. The cold start injector is continuous.

Think about it. It is extreeeemely unlikely that all injectors would start leaking simultaneously. It is extremely unlikely that the fuel pressure regulator would jam up shut to such an extent that the fuel pump could overpower the injector pintles (fuel pump has a check/relief valve). It is veeeeeery unlikely that a stuck AFM flap could signal the injectors to rinse the engine with gasoline when all it does is add maybe a few hundredths of a second.

I would use a tee section of pipe in the fuel loop to bypass the cold start valve, check the oil level (if high, change oil), stick in some fresh plugs and run that puppy clean. Then, pull the cold start injector and re attach the fuel lines but keep it unplugged. Stick the nozzle end towards a little container. Apply fuel pressure via the AFM wiper with ignition on. Any drippage or spray? Replace. No? Attach the plug. Disable ignition. Have assistant crank engine. Spray above 68* ? Replace thermo-time switch.

Liquid leakage at the exhaust manifold flange is not necessarily evidence of some dire exhaust leak. Within a couple of seconds of running, the clamping force increases. But do check for 15 ft/lbs torque on the nuts when engine is stone cold.
Colin

[vwlover77]

[It is veeeeeery unlikely that a stuck AFM flap could signal the injectors to rinse the engine with gasoline when all it does is add maybe a few hundredths of a second.

Well..... I had my injectors serviced by Cruizin Performance. After being cleaned, each injector delivered 77ml of fuel in 90 seconds of pulsed operation and that same volume of fuel in only 20 seconds wide open. That's no small amount of fuel!

Anyway. let's hope it's something as simple as the cold-start injector!

[Amskeptic]

[It is veeeeeery unlikely that a stuck AFM flap could signal the injectors to rinse the engine with gasoline when all it does is add maybe a few hundredths of a second.

Well..... I had my injectors serviced by Cruizin Performance. After being cleaned, each injector delivered 77ml of fuel in 90 seconds of pulsed operation and that same volume of fuel in only 20 seconds wide open. That's no small amount of fuel!

Anyway. let's hope it's something as simple as the cold-start injector!

With a running engine, yes. But if your engine is not running, is not capable of signalling the ECU to fire the 13 pulses per second at idle, then you are looking at an unlikely scenario of a stuck open AFM asking for fuel where the ignition pulse is saying we are only cranking at one time per second. Although, as I think about this situation, ANY injector could stick with a piece of crud and become continuous . . . yet, all plugs would not be wet in that scenario. I hope EZ Gruv fills us in, I am curious as heck.
Colin

[VWBusrepairman]

Well..... I had my injectors serviced by Cruizin Performance. After being cleaned, each injector delivered 77ml of fuel in 90 seconds of pulsed operation and that same volume of fuel in only 20 seconds wide open. That's no small amount of fuel!

Indeed it is not. Could be several things acting at once. Over pressure, injector pulsing longer than normal, timing issues, for example.

Don-your engine sounded great this weekend, by the way. Made me realize how bad my exhaust leak actually is.

[midatlanticys]

I've got no f/i experience to help with, but need to ask if the cold start injector activates on a warm/hot engine?

I'd also want to clean/dry up all the gas residue I could find and have someone crank the bus for a few seconds and then look for his royal wetness with plenty of bright light and open nostrils. Check everything again. . . . if nothing shows up try a few more cranks? How about another fine toothed comb over all fuel lines in a slow methodical search, even the 4 month old ones! . . . . just my .02 non-cents!

[Amskeptic]

I've got no f/i experience to help with, but need to ask if the cold start injector activates on a warm/hot engine?

It activates for less than a second at 58* and up to 11 seconds at 0* F only during cranking.
Colin

[EZ Gruv]

Update time.
I got the pressure gauge in the mail today and hooked it up. Looking at Bentley for specs, and it reads:

Disconnect the vacuum hose from the pressure regulator and plug the hose. Start the engine and observe the pressure gauge. The gauge shoud read approx 35 psi. If pressure too high or too low, replace

With the vacuum hose off and plugged, I get 35 while cranking.

If the fuel pressure is correct with the vacuum disconnected, repeat the test with the vacuum hose connected...gauge should read approx 28. If pressure too high or too low, replace

With the hose on, I'm still getting 35.

Sooooo, I'm getting too much fuel and flooding?
My new to me (used) pressure regulator should be here tomorrow...

[Gypsie]

Try applying 'mouth vacuum" -extra piece of hose to the vac port on regulator, and...uh...suck. This can be done with the engine off using the afm wiper to turn on the pump

Does the pressure change?

have you confirmed vac routing?

fuel lines to injectors tight?

just throwing things out there.

[EZ Gruv]

Try applying 'mouth vacuum" -extra piece of hose to the vac port on regulator, and...uh...suck. This can be done with the engine off using the afm wiper to turn on the pump

Does the pressure change?

have you confirmed vac routing?

fuel lines to injectors tight?

just throwing things out there.

I guess I'll have to try the 'mouth vacuum' and see what happens.
Vacuum routing is correct.
All fuel lines tight.

[Amskeptic]

Try applying 'mouth vacuum" -extra piece of hose to the vac port on regulator, and...uh...suck. This can be done with the engine off using the afm wiper to turn on the pump

Does the pressure change?

have you confirmed vac routing?

fuel lines to injectors tight?

just throwing things out there.

I guess I'll have to try the 'mouth vacuum' and see what happens.
Vacuum routing is correct.
All fuel lines tight.

Gypsie brings up a good point. All items on the same circuit can kill the signal to the regulator. This happens all the time with the EEC valve on the air filter killing the vacuum advance signal to the distributor!
The fuel pressure regulator shares a line with the decel valve.
Caution: the above fuel pressure regulator issue is unlikely to cause the symptoms described. If gauge said 60 psi, well maybe we would have a blocked off return line somewhere, you know, squashed flat by a jack-that-slipped-that-rammed-the-2X4-spacer-up-against-the-gastank-floor or sumpin..