1987 Ram 50 4x4 M/T 2.6L Quits when warmed up?

[Borgerding]

Hello all, Im new to the forum.
I recently picked up a 87 Ram 50 4x4 M/T with the 2.6L engine. It has approx. 250k miles on it.

Problem is: The engine starts up fine when cold, but after its warmed up, (a drive around the block), the engine dies. When I give it throttle to tryn keep it going, it bogs down, wont increase rpms, and finally quits.
It doesnt want to start up again until it has cooled down, (after an hour or so).

Previous to having this issue I did replace the timing/oil pump chains and guides. (Because 2 of the chain guides were broken). I took great care to make sure I didnt upset the timing, but I guess I cant totally rule that out?
I did a compression test and did discover that I have 100psi on 3 cylinders, and only 55psi on the 4th. I tested that cylinder wet and it did jump to about 80psi.
I know the previous owner, and the truck did run ok before all this, (although it did run a bit rough and did have a decent exhaust leak).
I noticed that there is no cat/o2 sensor on the truck, but the previous owner had been driving it like that for years.
After replacing the timing/oil pump chains, etc. I finally got it to start by spraying carb cleaner down the carb and into any oriface I could get to?
I understand this is a feedback carb, which worry's me, as It complicates trying to diagnose.
Any help would certainly be appreciated.

[tortron]

I think you want to do a leak down test to confirm you don't have a leak in your head gasket (these heads crack as well)

Could also be spark break down. Coils when they die work ok when cold, but as they warm up the begin to short out internally

[Borgerding]

Thanks,
I'll try the leak down test.
Regarding spark, I forgot to mention that I did replace the coil and distributor pickup coil.
I also have new plugs and wires I need to put in, as the existing ones seem quite old and questionable.

[Soular]

I have the same truck and its doing the same things... but it starts up again...just will not stay running... worked fine all weekend then monday as I drive it it was hard to start but I just thought it was cold then it started and ran until it warmed up and died... I drove it and I had to keep the revs up or it would die at a traffic control light or stop sign.

Even while on throttle you can hear it miss just a little... not much...but just a little rumble...but as soon as I come off throttle the Engine shuts down. I'm lost... I have a stock Carb and EGR I am sure they both need to be cleaned... looking for the proper technique so not to mess anything up.

I am going to change the plugs and wires... I have a new top part of the distributor ...I guess its the cap.... I will read up on how to install that...
If you have distributor... do you have a coil?

I was reading and Its hard to tell since their are some many version of the truck...

Thanks for the help!

May I ask ... did you every find out your issue? May thanks!

[FMS88]

[QUOTE=Soular;64558]I have the same truck and its doing the same things... but it starts up again...just will not stay running... worked fine all weekend then monday as I drive it it was hard to start but I just thought it was cold then it started and ran until it warmed up and died... I drove it and I had to keep the revs up or it would die at a traffic control light or stop sign....

Sounds like fuel is not getting to the idle circuit. Check the wiring harness to the carburetor because a bad connection could cause this problem. Separate the eight-pin connector to the carburetor harness that's on the driver's fender well to the rear of the ignition coil. Look for dirty or corroded contacts and clean as needed. Reconnect and test.

If that didn't fix it, test the cut-off/decel solenoid on the carburetor. On the carburetor (male) side of the eight-pin connector, locate the light blue and red-orange wires. The wires have the same diameter and their pins are on opposite sides of the pink divider inside the connector. Apply battery current to the pins of these wires (polarity isn't important). You should hear a click from the carburetor when the connection is made. If no click, the solenoid should be replaced because it isn't opening and that deprives the idle circuit of fuel.

[geezer101]

That cylinder #4 compression is suspicious. Go through all the top cover screws on the carb to ensure they're firmly tightened up but not stupid or you'll tear the screwdriver slots out of them and ensure the carb mounting bolts are tight as well. The O2 sensor isn't critical on the feedback systems but will affect fuel economy/power. All the vac control hoses can cause mayhem if they've perished or are split/leaking. Is the fuel pump still operating at a decent pressure? A tired pump can cause running issues as well. If the carb hasn't been stripped down in the last 15 years, it's overdue for a rebuild kit. This is not a job for a carb noob either. The Mikuni is no fun to work on and if the throttle butterfly plate is worn out and sucking air around the throttle shafts, it won't help putting new gaskets and seals through it. If you don't have to appease the EPA, it might be worth your time to invest in a Weber install kit but try to diagnose the problem(s) before throwing money at it.

[Soular]

Thank you so very much for this...I will give these things a try... so sorry or the late reply!


I have the same truck and its doing the same things... but it starts up again...just will not stay running... worked fine all weekend then monday as I drive it it was hard to start but I just thought it was cold then it started and ran until it warmed up and died... I drove it and I had to keep the revs up or it would die at a traffic control light or stop sign.

Even while on throttle you can hear it miss just a little... not much...but just a little rumble...but as soon as I come off throttle the Engine shuts down. I'm lost... I have a stock Carb and EGR I am sure they both need to be cleaned... looking for the proper technique so not to mess anything up.

I am going to change the plugs and wires... I have a new top part of the distributor ...I guess its the cap.... I will read up on how to install that...
If you have distributor... do you have a coil?

I was reading and Its hard to tell since their are some many version of the truck...

Thanks for the help!

May I ask ... did you every find out your issue? May thanks!

[Giovanni89]

The ballast resistor that feeds power to the coil can also fail in a similar fashion. Make sure your coil is getting 6 volts hot. The low compression cylinder is not good, but I think it should still run if everything else checks out ok

[geezer101]

^ +1 on that. Probably the most common failure in regards to a no hot start/random engine shutdown issue. The ballast resistor should be changed if the coil is a suspect as they normally come as an integrated assembly.

[Soular]

Hate to seem like a total New User... but where are the ballast resistor and the fuel Solenoid (which I think I have found, front left side on the carb,,, at least that where one group of wires seems to lead...

My guess to replace that guy I need to take the carb off... is that correct?

One other thing... when I unplugged that wire harness that sits on the fender with the wires that leads to the carb... the truck ran past the warm of phase... I hit the throttle and it came down (rough idle but it idle and did not cut off until I turned it off...

Then I hooked the wire harness back up and started it the motor and it would not stay running...

I want to do everything possible before spending any money on a weber as they are pretty expensive... thanks again all

[FMS88]

The ballast resistor is a white porcelain block next to the ignition coil in the center of the picture below:
21492

The cut-off fuel solenoid is on the left side of the carb, below and just forward of the throttle opener.
21493

You don't have to remove the carb, but you may need small vice grips to loosen the screw. After removing the screw and retaining clip, gently pry the solenoid out using a small screw driver. Here's the solenoid removed:
21494
Test its electrical function - it should click when energized. Clean the side and end ports and replace the 'o' rings if bad. Install it so the flat side is opposite the mounting screw.
With the carb disconnected and a cold engine, it will start if the solenoid is good or bad. But it should stall once the engine is above 150 degrees. So I'm surprised yours continued to run with the carb disconnected. The cut-off solenoid is the only in-carb electrical component that can prevent idling. It should still idle, maybe poorly, even if the other electric components (TPS, choke, feed back solenoid) are faulty.
One other possibility is a bad connection at the carburetor's computer located below the right end of the dashboard. Pull off the two connectors and look for and clean any corrosion.

[Soular]

Thank You So very Much!! I will give this a try.
This is so very helpful! Thank you!!!