1978 Bus - 2.0l FI Fuel delivery problem??

[MidWesty]

I was just getting read yto head out for the weekend and the ol' bus is not cooperating. She cranks pretty hard but doesn't want to fire.
Quick review of recent problems:
I got up one morning about a month ago, jumped in and drove the bus to work. When i went to leave it wouldn't start. Tried pushing it, jumping,, etc.. Went up and filled a gas can and she fired right up. The fuel gauge does not work consistently so I figured I just misjudged it. I went and put gas in the bus and all was well.
Fast forward to a week ago. The wife drives the bus to work. Starts fine in the morning, but when she goes to leave in the afternoon, no start. Same thing. I go get gas and she starts up.
To the best of my knowledge, there is no fuel leak. I've checked everywhere. The rubber on the gas cap is basically nonexistent though. I figured maybe with the warmer weather then expansion in the tank, or lack of it due to a bad seal, maybe the fuel evaporated?? I can't fill it up due to a leak in the filler hose somewhere. When it gets close to 3/4 full it starts pouring out of the tank or hose.
I just came in from trying to get it to start. We're 2 hours late to leave for the weekend and getting aggravated. I just went up and got fuel for it, it's a got a brand new gas cap. I checked the fuel filters, figuring running the bus out of gas a couple of times they may be full of garbage. Everything checks out. Pump seems to be working.
This bus ran fine for 3 years strong, with no real problems. I put it away for the winter, and she's been giving me trouble with this ever since.
I don't currently have a way to test the pressure in the system.
Any ideas, or anything I may have overlooked???

Thanks!
Steve

[MidWesty]

Update.
Just for kicks I put another 2 gallons of fuel in the tank. Almost. Got about half the container in when it started to overflow. I let it sit a minute to see if it was just back pressure or something. Checked back on it, the fuel is still in the filler tube. Now I'm really confused. Was I ever really out of gas, or was it a coincidence that it would start after putting fresh gas in? We may never know. I'm loading my Jeep up for the trip now so I'll have to get back to this sometime next week.

[Amskeptic]

Update.
Just for kicks I put another 2 gallons of fuel in the tank. Almost. Got about half the container in when it started to overflow. I let it sit a minute to see if it was just back pressure or something. Checked back on it, the fuel is still in the filler tube. Now I'm really confused. Was I ever really out of gas, or was it a coincidence that it would start after putting fresh gas in? We may never know. I'm loading my Jeep up for the trip now so I'll have to get back to this sometime next week.

This sounds like a possible vaporization issue. You might be evaporating fuel in the lines when the engine was shut off . A nice couple of cool gallons of outside gas might be cooling the system down enough to condense the vapor. If you'd like to track down this scenario, hook up a fuel pressure gauge. FI likes a residual pressure of no less than 14 psi after 15 minutes. Both the check valve in the fuel pump and the fuel pressure regulator is responsible for preventing vaporization during heat soak.
Colin
(sorry about the Jeep, really sorry)

[MidWesty]

Thanks for the info. I'll be picking up a fuel pressure guage tomorrow. What you explained would make sense as to why it starts up in the morning when it's nice and cool and then won't after sitting in a hot parking lot all afternoon.
I've never messed with the FI system on anything. Does the vehicle need to be running to test the pressure?

Oh yeah, that Jeep thing. It's one of those old pickup truck Jeeps. It's actually been a good beater. Talk about a menagerie of different parts makers though. Jeesh

[Randy in Maine]

Yes, the engine needs to be running to test the fuel pressure.

Might try this little test viewtopic.php?t=213 and suggest any changes to it to make it more understandable.

Did your bus sit for a while with dead gas in it for a few years before you got it? Dead gas plays tough with the various fuel delivery components (tank, pump, fpr).

[MidWesty]

Sorry it's ben so long. Life gets too big for me sometimes.
I've managed to make a pressure gauge and attach it to the fuel rail. Obviously in the heat of the day it's not going to start. (As determined earlier) But shouldn't there be pressure building while I crank the engine? Also when I removed the 7mm cap I tried to relieve pressure in the line by using the pump as directed in the link, as well as pulling the gas cap. There still seems to be a slight amount of pressure in the line because it slowly released fuel the whole time i was removing the 7mm cap. it actually did the whole time I was messing with getting the fuel pressure gauge hooked up. Normal?
2 other things I noticed as well. When I took off the gas cap, I didn't hear an exchange of air. I expected to hear something as it is about 90 deg. today. It's a brand new cap. The second thing I noticed was the fuel pump makes absolutely no noise at all. That seems odd to me. I had my daughter turn the key one click while I laid under the pump and heard nothing. I can feel it click if my hand is on it. I can also hear a very audible click in the engine compartment, but no usual whirring sound.
With that in mind as well as no pressure during initial cranking, is it possible the fuel pump is not pumping as hard as should could or is it a case of it either works or doesn't? No in between?
That's as far as time has allowed me to get. Won't be able to check for residual pressure unless I can get it started somehow. I'm gonna try tonight when everything cools down.

Thanks!

[Amskeptic]

I had my daughter turn the key one click while I laid under the pump and heard nothing.

Pump does not run in the "on" position by itself. It has to be energized by the airflow in the AFM closing some contacts to give the fuel pump voltage. The fuel pump is energized by the starter circuit as well. Both the starter and the AFM are signalling the double relay to send 12 volts to the pump. Get a simple test light on the + pump and ground the alligator clip on any good exposed metal. Have your daughter briefly engage the starter IN NEUTRAL and see if the test light illuminates.
Colin

[MidWesty]

I actually remember reading about doing that manually now that you mention it. I'll have to try later tonight when I get a chance.

Thanks!

[MidWesty]

So I performed the light test per your (Colin) and Bentley directions. In the Bentley they just have you run one wire of the light to the positive and the other to the brown (ground)negative wires instead of grounding the one wire. I tried both suggestions. When I followed Bentley's setup the light came on while cranking the engine. The other way, just clipping the wire to a good ground on the body it didn't come on. Not sure if it was just a bad grounding job or not. When I went back and wired it straight through like the first time, again, it came on.
I also tested the pressure while cranking once again. Still no pressure. Bentley says there should be around 35psi while cranking. I tried 2 different gauges to be absolutely sure.
So I'm guessing the pump is not working. But, how does that play into the bizarre temperature symptoms it was having?

Thanks for all the info so far!

Steve

[Randy in Maine]

Make sure your double relay is not the culprit. Otherwise I would say that the problem is in the fuel pump (as in not happening).

Randy

BTW, my daily driver is a 90 Comanche. Never was a Jeep guy although this is my 3rd one.

[MidWesty]

I managed to get a used pump from a friend for nothing. It was in unknown condition and had been laying around a while. before i disconnected fuel lines and such I hooked up the wires and had the wife crank the key. It quietly whirred away. I then put the wires back on the old one just to make sure. It did absolutely nothing. So I install the new one, with new filter and whatnot. Get everything cranked down nice and tight. Have the wife crank it over and fuel starts blowing out of it like crazy. I checked the outbound hose clamp and it was nice and tight. I moved the clamp up a little closer to the pump to be sure it was getting a good bite on it and try again. Fuel blowing out like crazy once more. The fuel seems to be leaking around the metal casing on the pump the best I could tell. I know they rebuild these things, is there something that can be done to remedy this? A matter of getting a seal kit perhaps?

Randy, your link to testing the pressure is good the way it is. Very easy to understand for the most part. I've had plenty of VW's but this is my first FI and I quickly understood the info in your write up.

'87 Comanche here with 80K original miles. Pretty decent little truck. Had to replace all the metal brake lines and master cylinder last week, and then somehow managed to lose all the hardware off the top of the driver's side front shock on my way home from a job?!?! Sounded like someone threw a handful of change out the window. No symptoms at all. Never seen anything like it.

Thanks for the help!

Steve