1986 GW stumbling and stalling uphill when warm

Stock FSJ Tech Area
jcpianka
Posts: 2
Joined: Sun Jun 24, 2018 3:53 am

1986 GW stumbling and stalling uphill when warm

Postby jcpianka » Sun Jun 24, 2018 4:40 am

hi all. Wondering if anyone has any suggestions or new ideas to try.

1986 Grand Wagoneer with a 360 2v and ~82,000 miles. It has been running great for three years (10,000 miles)after doing much work including new 2150 carb, fuel lines, vacuum lines... pretty much all stock.

~ one month ago started with issue of stalling while going uphill but only when it is warmed up. no issue when cold. I couldn't original determine if stumbled first so looked at electrical/ignition issues also. The truck will restart immediately while rolling in neutral after ~5 seconds of turning over, but stalls again on next gradual incline. if i pull over and let the truck cool down for five-ten minutes it will go until it warms up again. Fuel filter is warm to touch but not hot and you can hold it comfortably in hand. The fuel filter orientation is correct and vent tube has been checked to be ok.
After scouring this site (thanks) i have over last month done:

fuel filter x2, replaced mechanical fuel pump replaced, distributor pick up (stock dist) replaced, ignition coil replaced, Ignition control module (on fender under hood) replaced, coil wiring (replaced plastic cap with regular wire connections), ground wires, fuel tank pickup and "sock" (although it seems slightly shorter than one taken out), rubber fuel lines from tank to steel lines and from steel lines in front to mech pump. I moved the fuel lines a bit further away from engine and fixed a pinhole exhaust leak that was near the metal lines coming from the small air pump tubing. this happens with a full tank of fuel also and i've been putting high test fuel in it as that was also another suggestion relative to vapor lock. Ater reading many posts about vapor lock issues i wonder what would cause this all of the sudden. Truck is on Martha's Vineyard and temps have been mild/moderate and no major changes in fuel (10%e), and its been run in hot temps without issues in past. truck temp is normal.

recent work before this problem started includes that i lowered gas tank and painted behind it before having the entire truck professionally undercoated about a month before problem started, but put miles on it and drove on couple hundred mile trip off without issue.The gas cap "looks" ok but not replaced.

Kind of out of road here so any suggestions would be appreciated. thanks!

User avatar
will e
Posts: 3306
Joined: Sat Aug 18, 2012 8:21 am

Re: 1986 GW stumbling and stalling uphill when warm

Postby will e » Sun Jun 24, 2018 7:19 am

Welcome to the forum. It certainly sounds like a fuel vapor issue. Get a fuel pressure gauge and install it as close to the carb as you can. Even better if you can install the gauge in the cab. This won't fix your problem but it will confirm if you are having vapor lock.

Another possibility is the carb is getting too hot but I would suspect letting it sit for 5 to 10 minutes isn't long enough to cool the carb down. In fact, it probably get warmer.
81 Wagoneer - 'WILL E' Retired

82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau Moab Seats/RCI 6point Harness/Hella Aux lights/tuffy console/killer32 sliders/custom bumpers and roll bar/WARN 8000/steering brace/CB/dual batts/custom TC skid plate

letank
Posts: 2408
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: 1986 GW stumbling and stalling uphill when warm

Postby letank » Sun Jun 24, 2018 11:19 am

x2 as Will e said.

You can remove the gas cap to see if gas tank venting is obstructed.

Any difference between full and less than w 1/4 tank of gas ... hinting at a weak fuel pump...

Sorry, for the snide remark, but hills in MV? unless you are having fun on the sand dunes

welcome to the asylum
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (226 Kmiles... the running test lab)
See Engine bits and Fuel and brake lines, and Body work

jcpianka
Posts: 2
Joined: Sun Jun 24, 2018 3:53 am

Re: 1986 GW stumbling and stalling uphill when warm

Postby jcpianka » Sun Jun 24, 2018 4:29 pm

letank, yes you're so right, these hills aint Rt 89 in VT which it previously would bear through no problem....so funny though. certainly not much incline but stumbles and dies.

it happens when tank is full too and removing cap makes no difference. If it is vapor lock, i'm curious why all of the sudden and in such cool weather and light duty use where it has been fine will same setup for years in the same climate...etc.. Thanks for the reply(s). very much appreciated..

letank
Posts: 2408
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: 1986 GW stumbling and stalling uphill when warm

Postby letank » Sun Jun 24, 2018 7:40 pm

jcpianka wrote:i'm curious why all of the sudden and in such cool weather and light duty use where it has been fine will same setup for years in the same climate...etc.. Thanks for the reply(s). very much appreciated..


gas has been reformulated, in the 80's, I remember driving in AZ in 120F weather, and no need to pop up the hood when we stopped, engine would restart without issues.

back to your issue, as Will e said time for fuel pressure check, even a new fuel pump can be defective or something else is off. It can be excess fuel flodding the carb such as the carb float height being off or the carb inlet needle being loose on its seat.
you can even block off the return fuel line to increase fuel delivery
Last edited by letank on Tue Jul 03, 2018 9:41 am, edited 1 time in total.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (226 Kmiles... the running test lab)
See Engine bits and Fuel and brake lines, and Body work

User avatar
67GMC
Posts: 70
Joined: Thu Mar 03, 2016 5:17 am

Re: 1986 GW stumbling and stalling uphill when warm

Postby 67GMC » Mon Jul 02, 2018 7:34 pm

I had something similar with my 84. Did all the stuff you did, no help. Changed the control module-seemed to be better for a few days and then started doing it again. Also had long cranking when warm, would die under load when cool etc. Sounded like heat-soak or fuel related issue. On a whim, changed my plug wires and it stopped acting up all together and has been running fine since then. . I think the wires had poor contacts and spark was weak or intermittent. I know it doesn't sound like that could be the issue but worked for me.
My Stable:
1984 Jeep Grand Wagoneer, 360 V8, Auto, SelecTrac
1987 Jeep Cherokee (XJ), 4.0L I6, Auto, Selectrac
And a few more....


Return to “Stock FSJ Tech”

Who is online

Users browsing this forum: No registered users and 9 guests