Hello folks, I've been browsing this site for a few days now and so impressed with the knowledge you offer. I recently purchased a 1981 D150 that's in general decent shape. The truck idles high and somewhat rough, high enough to bang on the u joints when going into gear. I want to get my problem straightened out so I'm looking for help. From my research, it appears my carb is a Holley 6145 which is electronically controlled. On the air cleaner there is a electronic spark control unit. The truck also has a distributer with a vacuum advance hose. Truck also has a ballast resistor. So far, does all this seem compatible?
When I was looking at the truck for sale on eBay, the engine pic showed a vacuum hose missing from the diaphragm on the electronic spark control box on the air cleaner. I knew that was a problem. From browsing this site I see that it's important for that hose be connected to the proper port. From more observations on this truck, I believe someone lacking knowledge (like myself) may have messed with other vacuum lines and st this point I have no confidence any are correct. If I stomp the gas pedal to try and get it from fast idle it tries to idle low but dies after a second and will not restart till I touch the pedal again.

I've looked and looked for diagrams showing the proper connections for my particular application but have failed to find this info. Any help would be greatly appreciated.

Looking at the carb from front of truck I have vacuum ports on the left and right side of carb, maybe 3 on each side. I'll have to figure out the pic posting method and post them as soon as I figure this out. Thanks in advance for any help offered up.

Lenny

I couldn't get your picture to work for me, but here is a scan from a factory service manual identifying the vacuum fittings on a Holley 6145 carburetor:



Virtually everyone that has a vehicle equipped with a lean burn system removes it and replaces the carb and/or ignition system with non-computer controlled versions. It sounds like you have the variant of lean burn that controls the carburetor only. This is good because you can change the carb easier than getig into changing the ignition (although changing the ignition isn't that hard either).

If you are interested, I can send you a scan of the lean-burn service section from a factory service manual to help you get your system sorted. Send me a PM with your e-mail address and I will send it along.

Here is a vacuum diagram for a 1984 225 in a truck with an auto trans and electronic spark advance:



This will be close, but probably not an exact match to the hoses in your truck. Most likely your hoses are the PCV, the charcoal cannister, the EGR vacuum amplification system, the hose to the air cleaner for the heated air intake blend door, and the hose that goes to the computer.

Thanks Reed for your help! It appears that the idle speed adjustment is on the back of the idle stop solonoid? That screw doesn't seem to change anything.

Proper adjustment of the idle speed using the idle stop solenoid is more involved than just turning that screw. PM me your email address and I will send you a PDF of the lean burn troubleshooting and repair section scanned form a factory service manual. It includes instructions on how to adjust the idle speed correctly with a idle stop solenoid.

So I spent s few hrs on the old truck and made some progress. With Reeds help I completed the vacuum lines and am confident that system is proper. I pulled the spark plugs out and noticed that 2 plugs were white and the others darker, not sure what that means. I checked the points, cap, rotor and all looked like a recent tune up, like new. I still had the high idle problem so I disconnected the wires to the idle stop solonoid and adjusted the idle way down to where I thought it ought to be. After a few minutes of idling I noticed the rpms started surging and if I let it go it got severe. If I gassed it for a little bit the surging would go away but come back after a few moments. I left the truck today with this surging issue going on. Does anyone have any ideas what to look at concerning this surging issue?

Reed, if you still have the video of the truck surging, fell free to post it because I cannot.

Which two were white? Are they "ash/powdery" white? The others are darker...oily sticky darker, powdery darker, dark shaded?

I would worry a bit on the white ones that you are lean/vacuum leak at the gasket/ maybe a little coolant leak????

Not sure without pics...

Whoa, whoa, whoa.... Is your distributor a points distributor, or is it and EI distributor with a pickup? If either of the above is the case, you are going to be looking for a Holley 1945 to replace the 6145, and the vacuum diagram will change a bit....

Hopefully this will work:

Lenny's motor has the shakes


I texted with Lenny for a few hours today as he worked on his truck. He has a non-lean burn 1945 and someone swapped in a points distributor in place of the lean-burn ignition system.

Here is a pictures of his plugs:

Two plugs looked like there weren't firing but they were. The others varried from oily dark to tan. I do have points, weird hey!

Reed corrected me on my carb, it is a 1945

Just to make myself feel better I'm gonna check the port that feeds the dist. advance making sure I don't have vacuum there at all idle. If that checks out correct I'll change the fuel filter add some premium fuel maybe. Truck has been sitting for a few years now but old gas has been run out because I ran truck 20 miles and it runs out very well.

Fresh fuel yes, premium fuel is unnecessary.

Definitely...if you have access to 87 clear (100% gasoline), that would be my first choice.... if not then regular will do it, 92/super is a real waste with this engine....(higher octane is designed to supress detonation or "knock" and may not have as much "energy" compared to a true lower octane... since your engine isn't knocking/pinging...you don't need it per Reed).

You may need to check for a leak in the manifold gasket where you have the lighter plugs....I also will urge you to upgrade to a set of NGK UR5 plugs over the Champions....they are a better quality of manufacture and should provide a more uniform check on cylinder condition (if they were all sooty and black then I might suggest UR4 instead being hotter, but your plugs aren't bad if we can find the leanout on those 2 cylinders).


Thanks Reed for posting those, pictures are more than 1000 words and help us see what you see and help you.

What do you guys think about the surging in that video? Right now I am thinking a fuel issue (failing pump, failing float, clogged filter, or pickup) or possibly a problem in the distirbutor (malfunctioning mechanical advance, faulty condenser). But the surging is just so rhythmic and slow that I am not too confident in my guesses. What else would make the engine run like that? If the lean burn computer was still controlling the ignition I would say it was the computer hunting for the right time to fire, but the computer is disconnected and the motor is running points. :shrug:

He also has 18-19.5 inches of vacuum when the motor is not bogging down but it drops when the RPM drops. That makes me think it isn't a vacuum leak.

Maybe sticky valves from sitting?