Author Topic: Ongoing Mystery Stall Problem  (Read 3429 times)

Offline docsuess84

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Ongoing Mystery Stall Problem
« on: September 01, 2018, 04:42:28 PM »
We've had our 86 Suburban for a little less than a year. It was running like a champ. The past few months it has started stalling out randomly. Usually on a steep hill, but not always. We've tried all the usual suspects. New distributer, new carb, new ignition coil, new fuel filterThe fuel pump tested perfectly, both a simple pressure test and the test done while driving. We discovered the fuel lines were smashed between the car and the fuel tank when the previous owner replaced it, but that didn't matter. The shop could of course never duplicate the issue. I did notice every time it did happen the engine was running hot. Closer inspection revealed a leaking radiator. Had the radiator fixed, and went several weeks with no issue going up and down hills to and from our house. Until today. Stalled out in the exact same steep part of the street leading to our house. My workaround is pouring a little gas into the bowl, and that seems to be enough to get it going to make it back home. Does anyone have any suggestions? My mechanic is stumped and so am I, and I have no idea what the radiator would have to do with fuel supply.

Offline Rapid Roy

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Re: Ongoing Mystery Stall Problem
« Reply #1 on: September 01, 2018, 04:47:23 PM »
Welcome.
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Mopar by Birth
Chevy by Choice

Offline Irish_Alley

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Re: Ongoing Mystery Stall Problem
« Reply #2 on: September 01, 2018, 05:34:25 PM »
welcome from maryland

before we start guessing take a minute to read This
« Last Edit: September 01, 2018, 09:41:41 PM by bd »
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline docsuess84

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Re: Ongoing Mystery Stall Problem
« Reply #3 on: September 01, 2018, 08:15:06 PM »
Hey thanks for the reply, I'm not sure what happened with your link but it doesn't seem to work.

Offline bd

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Re: Ongoing Mystery Stall Problem
« Reply #4 on: September 01, 2018, 09:42:20 PM »
Try the link again.  We understand it's a 1986 model Suburban, but which chassis, engine and transmission combination?  Did you measure fuel pump draw and volume?
« Last Edit: September 01, 2018, 09:51:20 PM by bd »
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline docsuess84

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Re: Ongoing Mystery Stall Problem
« Reply #5 on: September 01, 2018, 09:54:30 PM »
Oh sorry. It’s a 1986 Chevy Suburban K20 Silverado, 350, 4x4. Is that everything? Carbureted engines are completely foreign to me. Never owned one before now, and hoping to put this dark chapter behind us.  It’s technically my wife’s rig, and she’s stalled in some really inconvenient places.

Offline bd

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Re: Ongoing Mystery Stall Problem
« Reply #6 on: September 01, 2018, 10:00:00 PM »
Thanks for providing that additional information.  I see that you checked the fuel pressure, but...

Did you measure fuel pump draw and volume?

          ...and what is the measured fuel pressure?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline docsuess84

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Re: Ongoing Mystery Stall Problem
« Reply #7 on: September 02, 2018, 10:26:14 AM »
I didn’t measure it personally, but the two shops I’ve gone to measured 8psi.

Offline bd

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Re: Ongoing Mystery Stall Problem
« Reply #8 on: September 02, 2018, 10:50:29 AM »
The next time the symptoms occur, temporarily remove the gas cap and see if the symptoms go away.  If so, the tank isn't venting.  How many fuel hose connections are there on the fuel tank?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Henry

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Re: Ongoing Mystery Stall Problem
« Reply #9 on: September 02, 2018, 11:00:17 AM »
Hi Doc:
If it turns out the fuel caps are OK and the tanks are venting properly, the other thing to check out is the fuel line(s) to the fuel pump...you may have a hairline split if the rubber hoses are old. A hairline split will open and close depending on the movement and attitude of the vehicle and when it opens, the fuel pump loses its draw temporarily. I had this problem with my 76 with dual saddle tanks and after feeling along all the rubber hoses very carefully and flexing them I found a split on one hose that was not visibly apparent...replacement solved the problem. Because of the location of the hoses they are hard to replace and hence tend to get neglected.
Regards,
Henry

Offline docsuess84

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Re: Ongoing Mystery Stall Problem
« Reply #10 on: September 02, 2018, 12:17:02 PM »
Funny you mentioned those things. I had my mechanic on the phone one of the times I was stuck on the hill. He had me remove the fuel cap to rule that out. They replaced the fuel lines when they had it in the shop and noticed some hairline cracking. I'm pretty sure they all got replaced but I'll have to check.

Offline bd

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Re: Ongoing Mystery Stall Problem
« Reply #11 on: September 02, 2018, 03:08:31 PM »
Make sure none of the hoses are kinked and measure the fuel pump draw (~20" Hg while cranking) and volume (>1 qt in 30 seconds of cranking).
« Last Edit: September 02, 2018, 03:11:20 PM by bd »
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline docsuess84

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Re: Ongoing Mystery Stall Problem
« Reply #12 on: September 02, 2018, 05:59:03 PM »
Not to sound like an idiot, but how do I do that exactly? And what tool(s) would I need to do it?

Offline VileZambonie

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Re: Ongoing Mystery Stall Problem
« Reply #13 on: September 02, 2018, 06:46:51 PM »
You need a vacuum/pressure gauge.

For volume test, you need to route the hose into a suitable jar with the ignition coil disconnected during cranking.

Make sure none of the hoses are kinked or have the ability to kink. Make sure all lines and hoses are properly routed.
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Offline JohnnyPopper

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Re: Ongoing Mystery Stall Problem
« Reply #14 on: September 02, 2018, 07:29:21 PM »
Sounds like vapor lock.

Is it a 4BBL Carb? If it's a Rochester, have you checked the filter that is part of the carb?

I saw what you did there with the wife comment... not a happy place >:(
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