rowdy235

Hi all,

Been working almost every weekend on my 78 dually (formerly a mirage motorhome). We decided to put off doing anything permanent with the cab (still trying to make up my mind on the way to go) but we've got a good temporary solution in place. In the meantime been focusing on getting the engine running a little better.

When we first got the truck out it would run okay but would not idle once warm. It would go down low, almost die, then rev back up and do the same. This would usually happen a few times until it would inevitably die. I know for a fact all the fuel is fresh because it was bone dry (PO had drained the fuel luckily). I've also mixed some seafoam in for good measure. We checked for vacuum leaks with a propane torch and didn't find any, but I think a more thorough search along with a bit of desmogging is in order.

I was able to tweak the idle up enough to where it doesn't die, but it also appears to be idling around 1k RPM (No tach so just going by ear). Obviously this is not ideal but at least you can drive it without having to worry about it dying at every stop sign The idle mixture screw doesn't really change much and it makes sense because I'm pretty sure its not even utilizing the idle circuit at that speed. Acceleration/power is good and it fires right up cold or warm.

Now, I've been reading a lot about the idle cut solenoid or anti-diesel solenoid. I had an issue with my old 82 where it would randomly blow the engine fuse. That truck wouldn't idle at all, it seemed like you just turned the key off when you let off the accelerator. The PO had put a jump wire on that in the event it blew, and when you plugged that in you could hear a noticeable click. On this one I unplugged the solenoid and put 12v directly to it and no click. Also (not suprisingly) no change in running. I'm thinking about pulling the solenoid out and checking it. Can you see it move if its good? Also I read somewhere you can take the O-ring off the end and bypass the solenoid, is that true?

This truck does have CA emissions. I'd like to do the full de-smog and weber but not in the budget right now. Will probably be stripping some smog stuff off (smog pump/related components) but leaving some as well (charcoal canister, EGR) until I can afford to do the conversion

One other question, we took it down the road and put it through its paces tonight (trying to blow the cobwebs out, been sitting at least 10 years). When we got back we popped the hood and noticed the header was faintly glowing (Yes, header. Don't ask why the PO put a header on a motorhome. I don't know either.) Seemed like the first and third tubes were faintly glowing. Is this normal considering we were going pretty hard? My cheap HF thermometer was maxed out checking it. However, appeared the coolant was only running 180 so on the bright side my cooling system is supposedly good.

rowdy235

So was just reading around about the glowing header. Looks like its indicative of running lean, timing retarded, or clogged exhaust. As the acceleration and power seem good I'm thinking its not a clogged exhaust and probably not timing (but I will check both, will likely be getting a new muffler and a "new cat" shortly. Its worth mentioning its a very faint glow, it was dark out and you could still just barely notice it.

I think I'm going to spend a lot more time looking over for any vacuum leaks. It just makes too much sense, won't idle and seems to be running lean. Any usual places to look for? Only thing we've done is unplug the vac booster and plugged the hose (no change at the time)

gillesdetrail

iTrader: (1)

I prefer to check vaccum leaks with carb cleaner or brake cleaner, check around everything from the intake manifold gasket, carb gasket and everything connected to intake manifold and carb, vacuum hoses etc. For the timing, they like a bit more than factory so try that to see how it likes it (with the vacuum advance disconected). A header glowing red could be from retarded timing or clogged exhaust.

rowdy235

Yeah, I'm thinking this weekend I'm going to go through and take some smog stuff off and in the process check for vacuum leaks. I've always just tuned engines by ear, but I'll hit it with the timing light and see where its sitting. I was already planning to redo the exhaust but maybe I'll bump that up on my priority list.

msane99

I was a tooth off once on dizzy on a 85 6m-ge supra and it lit that header up.

rowdy235

I just have a hard time believing with the timing off or the distributor a tooth off it would have good power. Of course anythings possible, part of the fun with these old rigs

83

Yeah glowing header and plenty of power might rule out a few things. My friend had a glowing header but also lacked power, and it was because mice had chewed a couple spark plug wires. This gets into the lean/rich argument that seems to sometimes pop up...Lean causes more heat. But overly rich means that the fuel isn't burning in the cylinder and is instead igniting when it hits the hot exhaust manifold, causing the manifold to overheat and glow. Which means actually you're not running rich, you just don't have the spark to burn the fuel. In the case of the mice, anyways...

When my fuel cut solenoid was acting up, the truck would randomly only stay running with gas. As soon as I let of the gas, it would die. I did something which included running a wire straight to ground, and that "solved" it.

Unless you're good with carbs, a new carb is inevitable. It's just the way it is. Even a lot of the rebuild places are very hit and miss. Weber is the way to go unless you've got an Aisin guru somewhere near you. I had bad luck with the mail-in carb rebuilders. I had great luck with Weber. Only carb I've ever had any success actually cleaning and rebuilding is an old motorcycle carb.

Starting to desmog will probably help. The propane method is a good one, and is what the local carb specialist in my town used to find leaks.

rowdy235

Well over the long weekend I did some more work on the truck. I pulled the fuel cut solenoid and the o-ring on the end was half-gone. I went ahead and removed it (the o-ring) for the time being. I don't hear any click when the key is turned so my next step will be to dig into the wiring (probably ground/ ign + to eliminate any issues). I also found a vac leak at the carb base so I'm putting in a new gasket there next. I'm having trouble with the desmogging trying to figure out what to remove and what stays. Makes it harder that my truck has A/C which adds a few other things for idle up. I'm thinking at this point it may be best to keep the smog until I can go with a weber.

rowdy235

Made some good progress over the weekend. I replaced the carb base gasket and got that leak solved. I went ahead and replaced all the vacuum hoses (well at least the ones I was keeping). Actually found another sizable leak on the brake booster hose (dryrot mainly). I removed all of the smog except the EGR (hooked up according to vac diagram for federal emissions) and the Charcoal Canister. Added a new PCV valve with a new grommet and hose to boot. Then I went around and plugged all the unused vacuum ports. If nothing else it looks much, much nicer and easier to work under the hood. I then started up and went to tuning. I got it idling fairly well around 800-900 rpm. However, it still is a little choppy. I'm going to try running the fresh fuel with seafoam in it through and see if that makes any difference once I have a tank ran through. For now its running plenty good enough to drive.

One issue I do have is dieseling. It diesels very badly after being driven for even a short amount of time. I'm going to replace the o-ring (currently removed) on the fuel cut solenoid and make sure its working properly (will rewire if I need to) in hopes that that will solve my problem. Another minor issue is popping in the exhaust when decelerating in gear. My 82 always did this and I never worried about it, but this truck just starting doing it recently. Any ideas?

Just so I can say I did something noticeable, we put the flatbed on this weekend too. Came out pretty nice I think

msane99

Looks Good!

That fuel cut O ring is Prolly causing that dieseling like you said.

rowdy235

Well I got a new o-ring for the fuel cut solenoid. Verified that the solenoid is working and I have power to it with key on. Put it all back together and seemed good, fired right up and seems to run the same as before. Between yesterday and today I put about 50 miles on the truck just mainly running around town. I put about 10 gal of fresh fuel in the tank with a half can of seafoam. It seemed like the truck kept running better and better the more I drove it.

But...

Still dieseling. Its gotten better but still not great. I'm fresh out of ideas at this point. Doesn't seem to be running lean/hot, my IR thermometer on the header is around 600-700* right after driving. The fuel cut solenoid seems to be working as it should.

Heres a couple things I was thinking:

AAP- If the engine was sucking fuel through the vac line that seems like that would cause dieseling. I didn't notice anything when I was desmogging/replacing vac lines but its possible. I've heard from some the AAP can be bypassed? is that true?

Carb- perhaps I'm not getting anything from the idle circuit and running off the primaries which causes more fuel to be sucked through after shutoff. Probably need to do a rebuild but will let the seafoam work for a while before going down that road.

Any ides greatly appreciated. Truck runs great other than that.

rowdy235

Well I tinkered with the truck a little more this weekend. Turns out the AAP was leaking, so for now it is blocked off. Dieseling is gone and seems to run better after I adjusted the idle mixture. Was thanked for my hard work by my starter taking a dump When I first got the truck running sometimes it would just click instead of starting. Cleaned up all the connections and it was working okay. But went to start it and no click no nothing. 12v at the solenoid. Was going to tear into it and figure out whats wrong but was only $40 for a reman at oreilly's, so I said screw it and just replaced it.

Went for a little cruise up in the woods to test everything out

13Swords

You're doin great Rowdy. Keep up the good work!

Jus' a lil info I learned on the AAP diaphragm. Before all my mess started, my AAP was leaking too. Replaced the diaphragm and even with it not hooked up to vacuum it made a yuge difference in the idle & driving quality. Seems the carb likes that AAP chamber space (volume) to be as designed; with the diaphragm leaking, there is fuel on both sides of it. Sure, it's OK blocked off & works, but seems to work much better with a solid diaphragm in it, even with the vac blocked.

Can't buy 'em separate for cheap, but they do come in carb rebuild kits. Rock Auto has some for less than $10 right now.

rowdy235

I actually already have a carb kit but just lacking the motivation to tear into it. I'm planning to rebuild the whole carb over the winter. It makes sense it would run better with a good diaphragm in there

rowdy235

Well not too much to report over the last few weeks. Truck has been running better and better, but of course a couple quirks have come up. I've noticed especially when the weather is cold once in a while the truck will sometimes cool down after warming up. (The temp gauge only gets up to the mark above the C to begin with, but I think thats a gauge issue). I decided to replace the t-stat in hopes that was the issue. I think what I found should speak for itself:


Yeah.. needless to say new t-stat installed (the right way) with a new gasket. Now warms up and stays warmed up. I also now have better heat, the only trouble is the cable is seized so the only way to adjust is to reach under the dash with needle nose. Of course here in the PNW we need the heat (or at least defrost) 9 months out of the year, and if it gets too hot I can just crack a window. So not really high on my priority list.

I am going to be reviewing the wiring schematic to see if I can see any common link between the fuel and temp gauge. The fuel gauge goes to about 1/2 when full and the temp gauge only reads just above C even with the t-stat housing at 180* per IR thermometer. Seems like there may be some common denominator that may be causing both gauges to read improperly. Both are usable as is but the fuel gauge in particular is very inconvenient .

In case anybody didn't catch it in my buildup thread I made a couple plywood boxes to sit under the front of the flatbed add some storage. I think they turned out very nice

rowdy235

Oh yeah, I forgot I also replaced my blinker/hazard flasher so they work now. With the LEDs in the rear the blinkers wouldn't flash, not enough current. If anybody ever needs to replace theirs its located almost square center of the dash, screwed to the firewall. Its hands down the biggest flasher I've ever seen, about the size of a deck of cards and twice the height. I was able to replace it through the radio hole (although a PITA if I may say so). I used an EP35 Flasher from my local parts shop, IIRC it was around 12 bucks. Its an electronic flasher so I had to run a ground wire (used one of the screws that held the original flasher in place) and cut the original connector off and use some spade connectors. Honestly, the hardest part of the whole thing was trying to crimp the connectors on through the radio hole as the wires were not long enough to extend past the faceplate and I was not in the mood to dismantle everything. I just used some double-sided tape to attach the unit to the bottom of the dash so it won't bounce around and come loose

Just a side note, I took my original flasher into the parts house and the part # on it cross-references to the EP35 flasher. I looked through all the flashers and none of them would match the original Toyota connector I could find. So likely you're going to have to cut the connector off regardless.

13Swords

Rowdy,

My heater cable isn't seized, but I keep it on heat all the time anyway, and I live in Florida! Glutton for punishment in August, me is.


Nice work on the storage boxes!

Toyota connectors - UGH. It's all that Nippon Denso stuff. I had the same problem with my fuel pump relay. The Toyota relay was $80 minimum (!), just to get the stupid ND connector that fits. Guess what I did?

Bosch 5 pin unit (works exactly the same, according to the wiring diagram), 5 pin socket with pigtails, crimp on spade lugs to pigtails, plugged em into the original connector one at a time. Whole shootin match cost less than 5 bucks & works perfectly. Also, I still have the factory connector, in case I ever find a boneyard relay to keep as a spare in the glove box. Just plug & go!

Me so smart sometimes; other times, not so much.

Great work man.

83

Yep, plugs make it really convenient to pull a whole series of wires at the same time. But so far as I know, there's no reason why they can't all be connected individually. I've had to do this on some of my vehicles, too, when a plug was corroded and causing voltage drop, and cleaning it didn't help. Just cut the plug out and do some splicing. As long as you use good connectors, insulation and a quality crimper, no reason it shouldn't work as good as new.