'76 stock FI overfueling when idling after long highway run (over an hour)

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jmstu76
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Location: Edmond, Oklahoma
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'76 stock FI overfueling when idling after long highway run (over an hour)

Post by jmstu76 » Sun Mar 19, 2017 12:12 pm

So as the title suggests, we are dealing with a bone stock '76 Westy. Took it out to camp with the family this weekend. Our destination was probably 100 miles away. We stopped around 30 miles from the destination for a potty break. I stay in the bus and let it idle, which is was doing fine for quite a few minutes. No lights on. Fresh fuel earlier in the day. Clean topped off oil. All of a sudden the idle dropped and it started to chug, idle so low the lights were flickering. I blipped the throttle and she died. Waited a few seconds and tied a restart. Started turned over very slowly but it started, coughing, running poorly, no throttle input helped and it died again. We were at a stop in the middle of a turn pike. I was able to get it into a place and unloaded the gear above the engine hatch. Everything was in place. Strong fuel smell from the engine compartment. No fuel leaks. I messed with stuff checking wiring and over things. We sat for about 30 minutes. I unplugged the cold start injector. it was a 70 degree day and heat soak was setting in. I tried to fire it and it fired right up. It did not chug when it cranked. Gave it a couple of revs and it felt normal. Shut it off. Reloaded the gear. Fired it up and off we went. Ran fine, but we were doing highway speeds immediately without any stopping or idling. Made it to the camp site. got the leveling blocks out to level up as it idled and it loaded up and died. waited for a bit. started right up and up the blocks it went. I do not believe I am overheating.

Left for home yesterday. Went straight for fuel first. No prolonged idling. Started up fine, ran fine. Fuel of fresh fuel. My plan was to take interstates all the way home with as little of stop and go as possible. My plan was working and we had gone 1.5 hours without an issue and were almost home when construction slowed the freeway down and she started to load up. I exited, working the throttle with dead spots while it attempted to die. hit a stop light and it was over. Dead. Pushed into a closed business drive way. Called for help.

Again I unloaded when help arrived , I tried to restart, again at least a 30 minute rest and she restarted, I punched her home hard. Made it home.

Now, it's loading up for some reason. This is a bus I have driven to Colorado and all over (From Oklahoma). What would cause it to overfuel at idle or low rpm settings. I think unplugging the CSV was a fluke, but could the cold start valve be leaking when very warm?? metal expands when hot and O rings get brittle and hard over time. I know fires are started by the CSV when pressure causes fuel to spray between the metal and plastic bodies.

Also, Could this be a temp II sensor type of failure??

I thought maybe a fuel pressure regulator, but it drives quite well until freeway warm after some time and idling/low rpm.

It fired up in my driveway today (with the cold start valve unplugged) and it idled for over an hour without a problem and the throttle response was crisp. Obviously it wasn't freeway warm but it was definately warmed up. No stumbling, just it's normal consistent idle..

SO....what could be causing an overfueling???? I plan to test the temp II and possibly replace if I can find one and go from there
James
1976 2.0L FI with Hydraulic lifters

Edmond, OK
(405) 623-2191

Jivermo
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Re: '76 stock FI overfueling when idling after long highway run (over an hour)

Post by Jivermo » Sun Mar 19, 2017 5:36 pm

I had a rather similar problem in 2013, that turned out to be a loose vacuum hose. At highway speed it would suck itself onto the metal tube, but when I backed off, it leaked, and pulled regular air in, causing the bus to run poorly. It drove me nuts. I finally found it, after a lot of heartache. Great learning experience, however. Bus Depot has the temp sensors, now.

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jmstu76
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Re: '76 stock FI overfueling when idling after long highway run (over an hour)

Post by jmstu76 » Sun Mar 19, 2017 6:25 pm

Jivermo wrote:
Sun Mar 19, 2017 5:36 pm
I had a rather similar problem in 2013, that turned out to be a loose vacuum hose. At highway speed it would suck itself onto the metal tube, but when I backed off, it leaked, and pulled regular air in, causing the bus to run poorly. It drove me nuts. I finally found it, after a lot of heartache. Great learning experience, however. Bus Depot has the temp sensors, now.
I have checked the vacuum lines. Found an end on one of the smaller lines that had swollen due to oil exposure I trimmed it. The line from the elbow in the AAR isn't the tightest so I wrapped some tape around the metal insert and it snugged up. I'm not saying it can't be a vacuum leak but would that cause it to overfuel? Maybe I should run new vacuum lines to the FPR.
James
1976 2.0L FI with Hydraulic lifters

Edmond, OK
(405) 623-2191

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Amskeptic
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Re: '76 stock FI overfueling when idling after long highway run (over an hour)

Post by Amskeptic » Sun Mar 19, 2017 9:54 pm

jmstu76 wrote:
Sun Mar 19, 2017 6:25 pm
Jivermo wrote:
Sun Mar 19, 2017 5:36 pm
I had a rather similar problem in 2013, that turned out to be a loose vacuum hose. At highway speed it would suck itself onto the metal tube, but when I backed off, it leaked, and pulled regular air in, causing the bus to run poorly. It drove me nuts. I finally found it, after a lot of heartache. Great learning experience, however. Bus Depot has the temp sensors, now.
I have checked the vacuum lines. Found an end on one of the smaller lines that had swollen due to oil exposure I trimmed it. The line from the elbow in the AAR isn't the tightest so I wrapped some tape around the metal insert and it snugged up. I'm not saying it can't be a vacuum leak but would that cause it to overfuel? Maybe I should run new vacuum lines to the FPR.
Any injector could be leaky, not just the cold start injector.
Test TS 2 cold and warm. 2500 ohms at room temp and falling down to 75 and less when warm.

Next time you suspect trouble is just about to hit, please jump out and get to the vacuum hose that leads from the intake manifold to the fuel pressure regulator/decel valve. Take it off the intake manifold while the engine is still running if at all possible, and let us know if the idle improves in that heat-soak moment.

Are you comfortable doing a hot engine fuel pressure test?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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jmstu76
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Re: '76 stock FI overfueling when idling after long highway run (over an hour)

Post by jmstu76 » Mon Mar 20, 2017 8:32 am

Amskeptic wrote:
Sun Mar 19, 2017 9:54 pm
jmstu76 wrote:
Sun Mar 19, 2017 6:25 pm
Jivermo wrote:
Sun Mar 19, 2017 5:36 pm
I had a rather similar problem in 2013, that turned out to be a loose vacuum hose. At highway speed it would suck itself onto the metal tube, but when I backed off, it leaked, and pulled regular air in, causing the bus to run poorly. It drove me nuts. I finally found it, after a lot of heartache. Great learning experience, however. Bus Depot has the temp sensors, now.
I have checked the vacuum lines. Found an end on one of the smaller lines that had swollen due to oil exposure I trimmed it. The line from the elbow in the AAR isn't the tightest so I wrapped some tape around the metal insert and it snugged up. I'm not saying it can't be a vacuum leak but would that cause it to overfuel? Maybe I should run new vacuum lines to the FPR.
Any injector could be leaky, not just the cold start injector.
Test TS 2 cold and warm. 2500 ohms at room temp and falling down to 75 and less when warm.

Next time you suspect trouble is just about to hit, please jump out and get to the vacuum hose that leads from the intake manifold to the fuel pressure regulator/decel valve. Take it off the intake manifold while the engine is still running if at all possible, and let us know if the idle improves in that heat-soak moment.

Are you comfortable doing a hot engine fuel pressure test?
Colin
I can test the Temp II. Positive probe on the connecting spade inside the plastic housing and negative probe on a known ground? Measured in ohms for resistance.

I can pull the vacuum hose to the FPR, but when it starts going downhill, it doesn't take long.

I have a fuel pressure tester. Years ago I tested the pressure at the port on the fuel rail. Can you describe in more depth what a hot engine fuel test would entail? Is it as easy as hooking up the pressure test and drive til fully warm then take the reading?
James
1976 2.0L FI with Hydraulic lifters

Edmond, OK
(405) 623-2191

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Amskeptic
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Re: '76 stock FI overfueling when idling after long highway run (over an hour)

Post by Amskeptic » Tue Mar 21, 2017 6:48 am

jmstu76 wrote:
Mon Mar 20, 2017 8:32 am
Amskeptic wrote:
Sun Mar 19, 2017 9:54 pm
jmstu76 wrote:
Sun Mar 19, 2017 6:25 pm
Jivermo wrote:
Sun Mar 19, 2017 5:36 pm
I had a rather similar problem in 2013, that turned out to be a loose vacuum hose. At highway speed it would suck itself onto the metal tube, but when I backed off, it leaked, and pulled regular air in, causing the bus to run poorly. It drove me nuts. I finally found it, after a lot of heartache. Great learning experience, however. Bus Depot has the temp sensors, now.
I have checked the vacuum lines. Found an end on one of the smaller lines that had swollen due to oil exposure I trimmed it. The line from the elbow in the AAR isn't the tightest so I wrapped some tape around the metal insert and it snugged up. I'm not saying it can't be a vacuum leak but would that cause it to overfuel? Maybe I should run new vacuum lines to the FPR.
Any injector could be leaky, not just the cold start injector.
Test TS 2 cold and warm. 2500 ohms at room temp and falling down to 75 and less when warm.

Next time you suspect trouble is just about to hit, please jump out and get to the vacuum hose that leads from the intake manifold to the fuel pressure regulator/decel valve. Take it off the intake manifold while the engine is still running if at all possible, and let us know if the idle improves in that heat-soak moment.

Are you comfortable doing a hot engine fuel pressure test?
Colin
I can test the Temp II. Positive probe on the connecting spade inside the plastic housing and negative probe on a known ground? Measured in ohms for resistance.

I can pull the vacuum hose to the FPR, but when it starts going downhill, it doesn't take long.

I have a fuel pressure tester. Years ago I tested the pressure at the port on the fuel rail. Can you describe in more depth what a hot engine fuel test would entail? Is it as easy as hooking up the pressure test and drive til fully warm then take the reading?
Yes.

Yes, put a little grease on the intake plenum nipple so it will pull off easily.

In depth? Hot engine? Fuel? Yeah, be very very thorough and careful!
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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sgkent
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Location: Citrus Heights CA (near Sacramento)
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Re: '76 stock FI overfueling when idling after long highway run (over an hour)

Post by sgkent » Tue Mar 28, 2017 1:04 pm

just as an FYI - when a cylinder goes too lean it will misfire. When it does that fuel ends up either being ignited in the exhaust by another cylinder, or it is burned in the catalytic converter, or it ends up in the exhaust fumes where it can be smelled. Thus what smells like too RICH situation can actually be a lean burn.

When your misfire occurs, you might try a cylinder balance test quickly to see if it is all the cylinders or just one etc.
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

Merlin The Wrench

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