I have a 1991 W150 with a 360 and auto. It has 91K on it, bought it 2k miles ago. It ran great for 2-3 months, now barely idles. Sounds like its not firing on all cylinders and some black smoke in a lumpy idle. In the last 5k miles it has had new cap, rotor, plugs, wires, fuel filter, I've run fuel injector cleaner through it. I have played with the timing, but turning the distributor slightly in either direction has no change.

I only run this on weekends and I can tell its just getting worse.

Any ideas? Thanks

 

could be a problem with the hall effects in the distributor

 

hmmm.. black smoke usually means a rich condition to much fuel...or not enough spark or hmm bad new plugs/ not correctly gaped. <---im guessing at those ... do you have a vacuum gauge you could check the engine vacuum with...its worth checking if you havnot done so already

 

Remove the air cleaner, start the engine, and look inside the throttle body. At the bottom of both injectors you should see a cone of fuel. The cone should be solid with no gaps or streams and it should reach the sides of the throttle body throat. It is best to check the spray pattern in as little ambient light as possible and I use a flash light. The light shining on the cone shows it best.

 

Thanks. The plugs are new and gapped at 0.035 as spec'd. I have verified both injectors are spraying a nice cone. I don't have access to a vaccum gage.
I borrowed a code reader and get a code 33 (AC clutch, but I don't hve A/C) and a code 37 PTU solenoid. Trying to locate that today on the vehicle. Has anyone had to repalce/trouble shoot that code or a PTU solenold?

thanks

 

I have that code but I don't have that system on my truck. The solenoid is located on the inside of the drivers front fender just under the hood spring with 1-3 other solenoids. I have seen it to be the one closest to the drivers seat.

 

Replaced coil, hall effect sensor, plugs and fuel filter. Checked timing. What I found was leaky fuel injectors. I was leaking fuel into the throttle body. I tried new o-rings on the injectors, no luck. I replaced the injectors with the same leaky issue. I am not sure if I need to replace throttle body now? Has anyone had issues with not being able to seal the fuel injectors? I used vasoline to lube then and insert them.

 

I have had problems also. You must examine the o-ring sealing surfaces in the throttle body for scratches. This is very hard to see and I would recommend some sort of magnification be used with a lot of light. If you can't find any scratches, replacing the throttle body is not likely to cure the problem.

All o-rings are not the same even if they are the correct size. You must use the proper ones, I am not saying you didn't but I have seen others do it and am just trying to be comprehensive. The injector o-rings can be a pain to install properly. Usual causes for this are:
1. Someone scratched the injector o-ring grooves while removing or installing the o-rings. Never use metal picks for o-ring install or removal.
2. Something was not totally clean during install.
3. The o-rings were nicked on installation.
4. To much or no lubricant was used during install.
5. The o-rings were stretched too much during installation onto the injectors.

What does the spray pattern look like? If the pattern is good I would look at the o-rings. If the pattern is not good the injectors are the problem. Even replacements can be bad if they have been allowed to set around long enough between build/rebuild and installation. If the truck being down for a while is not a problem I prefer having the injectors rebuilt locally to insure freshness.

 

I just went through a similar issue on the same engine. I pulled the injectors while cleaning the throttle body, and did not get them seated properly on the first go. It was slobbering fuel out the top and dripping down from the nozzle end.

I pulled them out again, cleaned everything up really well, and lubed the o-rings a little better. I can say that it took some serious down pressure on the caps to seat them, and to keep the pressure on while tightening the hold-down clamp.

Push them in by hand until the plastic cap is flush with the upper bore flange, and keep pressure while tightening the clamp. Don't suck the clamp down too hard without keeping pressure on the injector caps or you can end up with the injectors shifting sideways (slightly) in the bore. Bit of a corny system for installation.