78' Scout II 4 cyl. issues?

wiggins

wiggins

Member
I have a 78' Scout with the slant 4. It has 52,xxx original miles and cranks and runs great. The problem is when I kill it. It refuses to quit, but not in a good way. It diesels out once I ve turned the ignition off until it chokes it self out. I figured I had a timming issue but it is set at tdc, perfect.(unless I am timing wrong? Off #1 and plugging the vac adv line?) I have adjusted the carb out and nothing worked so I determined that it must be the carb. I let a local shop rebuild the carb and they said the carb was slightly slugged w old gas but not bad. They rebuilt it but the problem still exist. It does not always deisel now, but if it does not, it sounds like shotgun coming out the tailpipe(backfire). I am wondering if it is still the carb, accelerater pump ect..?, or something else?
 
Where do you live and what is the typical fuel supply for this vehicle?

Does this vehicle have to be smogged?

Are all vacuum-operated systems in operational condition right now?

Is the hot curb idle speed set to correct specification? Does the curb idle speed change when the ignition switch is turned off (it should)?

If you expect the curb idle speed adjustment to perform correctly, then all oem systems must be in place and operational.

Most likely the curb idle system is not set correctly (assuming it's using a electric curb idle adjustment) and the base timing is too retarded.

Post a picture of the curb idle side of the carb so I can see it.
 
I live in east texas where the gas mix is up to 10% ethanol. It does not have to pass smog. All the vaccum systems work to my knowledge. I will need a little help from here on, I am not familiar with curb idle speed? Or hot curb idle speed?it is an electric choke but not sure again about the electronic curb idle adjustment. You just went a little over my head, but I appreciate your help. I'll get a pic as soon as I can, thanks wiggins
 
Once I get some pics, I know we can work through this.

By the way, I'm 5th gen texian, my kids live up between clarksville and new boston. My folks are still kickin' in hurst.
 
Boy are you missing out, texas is great. I 'll get a pic soon and thanks again for your help. Tried to load a pic earlier for my avatar and couldnt figure it out so I May need help with that as well. Damn newbies, I know!
 
You can send all the pics you want to my email and I'll post until you can figure it out:

michael@IHPartsAmerica.com

We try and stay on top of most any technical issue immediately. That does not always happen, but right now we're caught up and can stay pretty much on top of stuff. A few more days and the entire season begins to grow in it's normal fashion!
 
Ah much easier thanks. I also run premium 93 oct gas in all my old cars, could this be an issue with this 4 cyl?
 
Here's on carb pic.

And this one was rebuilt?? How long ago was that? Sure hope it looks much nicer inside!

The hot air tube from the exhaust manifold to the choke cap has been added I believe, you would not have both a hot air feed and an electrical feed to the choke.

So...if the actual choke cap operates as it should, I'd loose the choke tube completely, just simply take it off and leave it alone.

It should have a prestolite electronic distributor, please confirm that. If so, then if all vacuum systems are still installed, I'd "power time" the engine as described in this thread:

http://www.forums.IHPartsAmerica.com/ignition-tech/2122-ignition-power-timing.html

Since the rig does not have to be smogged, simply set the base timing where it runs best without knock/ping.

Once that is done, then adjust the curb idle speed to it's proper position of 550rpm. Then...play with the idle mixture screw run it in and out slowly until you achieve best idle quality. Then set the base idle speed one last time.

Do all the above first and then get back to us with the results of what you found out!

The vehicle does appear to be "stock" at least from what I can see in this pic. Please explain any other mods if it's not stock.
 

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Will do and yes as far as I know its all stock. I'll check the dist. Carb was rebuilt about 3 weeks ago by a local mechanic. I was not impressed w the outer apperance either. Get back to you soon on the rest. The hot air tube May be a mod. This thing was owned by a nasa engineer in the 80's-90's and I have found several little maintanace type mods on this Scout.
 
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Ok heres what I found. I was going back through everything and found 2 vaccum lines were crossed. 2 line coming off the vaccum tree, one was supposed to go to the idle speed sensor on the fire wall and the other was supposed to go to the air cleaner temp sensor. I fixed the lines and then went back through everything as you said. I took the Scout on about a 10 min trip came back killed it and perfecto! So I drove it on a 40 mile round trip. I killed it half way and no back fire or dieseling. So I drove it back home. When I got home and killed it I got a small poof out of the tailpipe, not a back fire just a muffled poof. So we are much improved but not perfect. I am not sure of the make of the dist. Bc I can not find any identifying markings. I'll send you a pic but I do belive it to be original. It also had a plastic cap that sperated the rotor and cap from the points, I have never seen that before. Also the heat tube looks original, tell me what you think? The choke housing has a threaded hole that accepts the tube and the exhaust manifold has a 7/8'' nut with a hole in it for the other end of the tube. I was going to just remove that nut a put a plug in the the manifold but the nut is more like a temp sensor and will not come out of the manifold. It May just be carbon build up but I did not want to force it.
 
That is a Holley gold box ignition system.

The part on the bulkhead that is leaking is the "gold box" and is failing now, that is why the potting material is running out of the back of it. These normally don't fail at once, but over time. Starting off with occasional hard starting...progressing to engine kills and then will re-start and go on after some time.

The pics I have now show this to be pretty much a stocker, so I'm assuming you want to keep it like that? That's fine, we'll just fix whatcha got now.

I'm not saying that your carburetor doesn't need some help, but let's make sure the ignition system is correct first. We have new amplifiers (part on the firewall) in stock at the shop now. Once it's replaced and you do the "power timing" thing again, then we can get back to the carb. Do not screw around with the carb heat tube, that is not the issue we have currently!
 
Yes definately keeping it all stock. I'll get the part ordered tommorow, thanks. For future reference was that a prestolite dist. Or could you tell?
 
Ok well to throw you a curve. I looked at the new gold boxes for sale and saw that they were actually gold and I knew that in no way was mine ever gold so I took a closer look and my box is stamped with a part # swf 4240 and prestolite is printed on the bracket to the box. If this part is available I would prefer to keep it original. Also the sticker under the hood on my cowl calls this box an engine speed sensor? As a side I noticed that this sticker lables the car a 196ci Scout II xlc, what is xlc?

Ok I read your thread and now I am more confident that I have a prestolite distributor. It is square for about 2 '' below the base plate
also mine looks more like the pic of the idn 4000 series you have pictured. Did they make these for the 4 cyl.? Has the red/brown/white wires
 
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Xlc stands for extra load capacity. Beginning with m/y 1975 it was ihc's way of dealing with the new federally mandated fuel economy requirements of the day. They upped the weight rating of the springs to increase the gvwr of the Scout so that it would be exempt from the most stringent requirements of light passenger vehicles.
 
wiggins said:
ok well to throw you a curve. I looked at the new gold boxes for sale and saw that they were actually gold and I knew that in no way was mine ever gold so I took a closer look and my box is stamped with a part # swf 4240 and prestolite is printed on the bracket to the box. If this part is available I would prefer to keep it original. Also the sticker under the hood on my cowl calls this box an engine speed sensor? As a side I noticed that this sticker lables the car a 196ci Scout II xlc, what is xlc?

Ok I read your thread and now I am more confident that I have a prestolite distributor. It is square for about 2 '' below the base plate
also mine looks more like the pic of the idn 4000 series you have pictured. Did they make these for the 4 cyl.? Has the red/brown/white wires
Click to expand...

Yes there are four cylinder prestolite distributors used also.

You are correct, I'm wrong! That is a prestolite unit. However, the device mounted to the firewall in this pic is for what??? I don't know.

By the way, the so-called "gold box" was also made with black covers and silver covers, but I've not seen any of the black or silver units actually installed in a Scout II...yet.

I believe that box on the bulkhead is actually for "engine idle" (part of the emissions system) but I can't locate anything about that right now, I'll keep looking. Simply pull the vacuum hoses off and use a straight nipple to connect together. Then go out and try it. If that makes it worse, then put a plug in each connector and try again.
 
I can do that, thats how I typically fix everything! Lol trial and error. The sticker on the Scout that shows all the vaccum lines calls that box an engine speed sensor. It is all electric but bolted to the bottom of this unit is a "vaccum pot" that the 2 vaccum lines go to. Coming out of the wiring harness that goes to the engine speed sensor is a seperate pigtail that plugs into the "vaccum pot". So the vaccum pot is electric and vaccum operated?????
 
wiggins said:
I can do that, thats how I typically fix everything! Lol trial and error. The sticker on the Scout that shows all the vaccum lines calls that box an engine speed sensor. It is all electric but bolted to the bottom of this unit is a "vaccum pot" that the 2 vaccum lines go to. Coming out of the wiring harness that goes to the engine speed sensor is a seperate pigtail that plugs into the "vaccum pot". So the vaccum pot is electric and vaccum operated?????
Click to expand...

I dunno!!!

This is a new item to me and I'm still doing some research!

But what I suspect is... At some road speed vs. Engine temp, the box does something which creates an additional vacuum "leak" in the fuel/intake system. That in turn does something with the intake charge for a period of time until; the system turns "off" again.

In your case, the system May actually be failed right now so it's turned "on". Let me do some additional research on this.

It's always something new around here, when IH "changed" stuff, there was really no mention of this except as part of a service letter that went out to dealers. We do have some of that stuff, but the majority is simply laying out there somewhere. A few of us know where the majority of it actually is but getting the folks that have the stuff to turn loose of it in some manner has not been successful.
 

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