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I was given a really beat-up, neglected '78 LUV long-bed Mikado for free. It was due to be scrapped in a towing company's yard, but the owner thought it ran too well to crush. He took pity on me because he'd towed two of my cars back home in one day. I was grateful for the three days this little LUV got me to work, but this morning it barely got me there, and didn't get me back. Looks like maybe my tow truck guy was sowing the seeds for more business. (OK, uncharitible thoughts like that are unfair, since he was really wanting to help.)

The problem is that it has run fine for the first few minutes of each drive, then starts to stumble as the engine heats up. The stumble has seemed speed related, and slowing down allows the engine to smooth out again. The problem is that I've had to drive progressively slower to and from work each day. This morning's drive ended with a leisurely crawl into the office on city streets at 30 mph or less, with occasional stops at the side of the road to let the engine smooth out. The truck didn't make it out of the parking lot at work, and a pressing appointment resulted in us leaving the truck there when she came to pick me up.

I've read through a dozen or so threads, and none exactly match my symptoms. Has anyone run into this problem? If so, how did you solve your problems?

I should mention that I've changed the fuel filter, and the air filter, both last night because I had them on hand and it seemed like the most logical thing since this seemed like a fuel pressure problem. I intended to run by the auto parts store on my way home tonight to pick up the usual tune-up parts in the hope that this is electrical in nature. I'm still torn about whether this is most likely a fuel pump problem or a coil or condenser problem. I also got looking at the manual and realized that my Series 8 carb has compensation for hot operation built in, and there is potential mayhem there too.

Oh, too many potential failures, all with similar failure modes... it's got my head swimming.

So, can anyone help? Thanks for any ideas you've got.

Scott

i would rebuild the carb and if that doesnt fix it, i would get a new fuel pump, if that still doesnt fix it them im stumped

i'll say it...vacuum lines I'm still finding hoses on mine that seemed ok that turned out feeble and your distributor could be wobbly.Theres an o ring on the shaft(tape the shaft to keep from nicking the replacement)and a gasket ring thats supposed to be under the cap.you lucked out on getting it it just needs TLC,good luck!

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Dr. Frankenstein

Sounds like fuel delivery problems to me. Was there a load of crud in the filter when you changed it? I always dump the filter out into a clean dish or at least a paper towel just to see. Dump out the end of the filter facing the tank and you get a good idea of what sort of stuff it might have picked up.

Also, there is a screen in the top of the carb. You unbolt the part that the fuel lines hook to right at the carb. There is a bolt that goes through that little hose manifold deal into the needle valve. Pull that bolt and the thing should lift off. The screen is a cylinder shape that fits inside it. If the whole works turns, you are unscrewing the needle valve and all, just the bolt should turn to get at that screen. Could be some junk in the lines has you clogged up.

If its not blockage, the pump is probably going bad. I've gone through a number of them in my time, never had much luck salvaging them. You can remove one end of the pump to get at a filter inside and try to clean it, but my luck has alway been that the pump was the problem not the filter inside it.

You can check the pump for flow by disconnecting the hose at the carb and putting it into a clean jug. It should run at idle for at least 30 seconds or so and you can get an idea of how many GPM you are getting. It should flow a pretty good stream if the pump is strong, but I forget how much in gallons it should put out.

Sounds like you got a gem if you can just get the crud gremlins cleaned out. This is not uncommon on a truck that has sat for a long time. The gas evaporates out of everything and leaves varnish behind that clogs pumps, lines, and carbs.

I forgot to mention, you should also check the points in the distributor. They are probably due to be replaced even if not the source of your troubles. Them being screwed up can cause a similar symptom though. While you have the cap off, scrape the contacts inside it to get the build up off them and the edge of the rotor. That won't hurt matters any either.

I had pretty much the same problem with my truck. I kept thinking it was the carb. So i rebuilt it twice and that still didnt fix it so i replaced the fuel pump and filter twice and still no luck. It finally turned out to be there was rust in the gas tank that kept floating over the hole and blocking it. The truck would idle fine but sometime when i would give it gas it would starve and almost shut off. It could be your tank so i would check that. If you have to then pull it and have a radiator shop boil out the tank and that will clean everything out of it.

Well, I'm glad my instincts are sound. I thought the fuel pump was inside the tank, but I went out and found it mounted atop a frame crossmember. It's an old SU looking pump, and I haven't heard any slow "chunk thunk" sounds from a working SU fuel pump, so that is now at the top of my list. The NAPA guy has a solid-state pump for $35 that I want to try next.

The idea of floating crap in the tank seems all too plausible. I'll drop the tank and clean it out. That idea about boiling it at a radiator shop is a good one. Thanks.

I've also called over to ask about a rebuild kit for the carb. They've got two part numbers for that, and I need to find the carb's model number to know which one to get. Anyone know where that number is cast or stamped into the carb?

If the pump and carb work don't straighten this out, my next line of attack will be the distributor and coil. I don't have an O-ring under the cap, but I have a flash shield. Is there an electronic ignition kit for these distributors? Oh, any recommendations on coils?

Thanks again for the advice.

Scott

if you want electronic ignition i would look for a more modern luv or pup, my 83 pup has electronic inition and it should be the same motor as yours

Changing out the points in the distributor is a quick and cheap thing to try before tearing into the carb. I think the last set I bought was about $8 and it takes me around 2-3 minutes to put a set in. (Had a truck that ate them monthly, so I'm well practiced). You need a feeler guage and a screwdriver, it would probably take you 15-20 minutes if you've never done them before. Recommended replacement for points (per the service manual) is only like 12k miles and most people don't do it anywhere near as often as that.

Rebuilding the stock carb is a really dicey endeavor. I've heard a lot of stories around here about rebuilt carbs running worse that they started, and people never getting them quite dialed in right again. If it were me, I'd run through as much other stuff as you can before jumping into the carb. Even new those stock hitachi carbs are held together by one part voodoo, one part happy thoughts, and one part gremlins.

Friday night while I was waiting for my wife to pick me up (the truck broke down at work) I tested the spark delivery by unplugging the #1 spark plug wire while the engine was idling. For the moments when it was idling smoothly the spark jumped across the gap nicely with a clear "zup zup zup" sound, but when the idle grew ragged the sound of the spark disappeared altogether. Hearing that I was amazed the thing was running at all.

Saturday morning I returned with my multimeter and tested the coil and found its primary and secondary circuits had the same resistance at about 1.6 Ohms... the secondary should have 1000 times the primary's resistance. So, my coil was bad too. The points were burnt and the resulting gap was too narrow. I figured the points were burnt because the condenser was bad. I headed to NAPA and bought new points, condenser, coil, cap, and rotor (not bad at $38 altogether). I returned and put them all in and the truck ran, and runs, like a champ. Oh, the condenser that had been in the truck was way too small too, which I'm sure contributed to the problems.

So, no fuel delivery problem. It was all spark.

Thanks, guys! Your advice saved me the cost of an unneeded fuel pump.

Scott

check the compression on the engine.. i had a problem similar to that and it ended up being the head gasket. mabe its running ok till the engine hets warmed up and parts begin to expand, also check plugs cap rotor wires al that stuff. I had a carbon tracked cap on my other truck and it ran terrible at road speed.

I had this problem. I went on eBay and bought a new Carb and had it rebuilt and put it on. Viola! Problem disappeared. The old Carb I gave to a friend to rebuild, which will probably be a while before he does it.

Sorry to say, it needs a carb.

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glad to hear shes back on the road

everytime i log in to this site my knowledge for cars goes up 10 notches