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IMP #669 repair resto thread

Idaho IMP

Member
Ok so I’ve been here for a bit. I thought it was time to start an ongoing repair thread for IMP 669. This was the unit and matching trailer for sale during the holidays on KSL. The family and I did a 1200 mile round trip to pick it and it’s matching trailer up. We’re in Southern Idaho. The cat was in Northern California, northeast corner.
On the day of pickup, I had to swap out the old hubs on the trailer so I could use a set of 6 lug trailer wheels I had from my deck over trailer. The condition of the old 14.5” tires on the trailer was bad. They would not have made it 100 miles. I ordered a set of conversion hubs through R and P carriages that would fit the #42 spindles on the old axle. I pre-packed the bearings so all I would have to do is remove the center nut, and pull the old wheels off, Install the new 2-1/4“ inner seal, and bolt new hubs on. Piece of cake. I had both sides rebuilt and towable within an hour. The trailer lights were completely shot. I’ve never seen wire insulation turn to dust. Luckily, I had brought a pair of magnetic tow lights, so I slapped ’on after loading the cat.
Now for the good part. The Imp was about 6 miles down the road, and 4 miles up his access road, dead. He hadn’t had the chance to install the new carb or alternator. Sooo, I towed the trailer up the road to the cat. Oh yea, there was a solid foot of snow on the road. Parts of the road was over 10% grade, so we had that going for us. Luckily there was a wye in the road where I could get turned around, to load the cat. I brought a 4000# come-a-long and a bunch of rigging goodies to load the cat. We drug the cat down backwards with a recovery rope. I then backed the trailer right up to the cat, tilted it down, rigged up the come along, and proceeded to yank the imp onto the trailer. It wasn’t easy, but I got loaded. by now it was getting close to dusk, so we headed out back towards Burns, Oregon. The trailer did great, it towed like a dream. We made it back to home the following day without incident.
 

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Idaho IMP

Member
Time for an update. After better temps and a bit of time, I was able to get the new Weber carb installed. It was an easy install. I had to flip-flop the final linkage rod as the new bracket was slightly different and underslung below the fulcrum. I had rigged a temporary choke cable to get it started. The carb came with 2 steel spacer blocks and fiberboard gaskets. The Weber does require a constant power lead, so I ran a permanently temporary wire from the ignition circuit. I found a 2” diameter scat hose on the Flea-Bay, as well as a silicone elbow to connect the carb to the original Donaldson oil bath filter behind the dash. For purposes of starting the engine and dialing in the carb, I ran without a filter. It fired right up! After being warmed sufficiently, I noticed a pretty decent stumble so I started looking at everything and discovered the plug wires were ran in numerical sequence, not in firing order. Wires were re-connected in proper firing order and engine runs smooth now. the Imp has 1154 hours on it. I‘m fairly certain the PO ran the cat with wires in sequence for who knows how long. I’ll be performing a full tune up shortly and installing a Pertronix ignition. The plug wires look original and they are hard as a rock. More to come shortly. I’m still in the discovery stage on this machine. Every time I turn a corner, I notice something else that needs to be fixed.
 

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Idaho IMP

Member
Man, you got that right! I have to say that these purpose built thiokol trailers are the ticket for maintenance. It has a square section on the tail for the rear end to clearance loading backwards but can be used to drain the engine and trans. they’re like having them on a car lift. it puts all the track components at a good working height.
 

Idaho IMP

Member
I spent an hour or so drinking around with the carb. I‘d like to hear others experiences with the Weber 34. Disclaimer: I’m in need of a major tune up, but it seems like this loves the choke, even after engine is sufficiently warm. The idle mixture is set at 1.5 turns out, and idle is set to about 1000 rpm. The engine will die if I push choke cam all the way to the stop to open choke completely. Im thinking these carbs take a while to warm up. FWIW, we got down to 15 degrees last night but hit 40 degrees this afternoon. Cat sits outside, but in direct sunlight. It will fire right off with choke when cold but also needs min. 1/2 choke to restart when “warm“.
 

Idaho IMP

Member
Also, I replaced the original Motorcraft voltage regulator with a standard. My charging problem is now fixed. Voltmeter says output is over 15 volts at Alternator lug. I plan to rewire the cat at some point in the future. There is a bunch of old crunchy wires and connectors. I’d like to clean everything up and add a master kill switch on the positive lead, as well as an ignition relay.
 

Cidertom

Chionophile
GOLD Site Supporter
I'd start by cleaning the carb jets. likely they got fouled by bad gas, sitting gas etc. Having to run with choke says you need more gas to keep the mixture correct.
 

Idaho IMP

Member
I'd start by cleaning the carb jets. likely they got fouled by bad gas, sitting gas etc. Having to run with choke says you need more gas to keep the mixture correct.
The carb is brand new, behind a brand new inline filter. I’m thinking there could be some crap in the inlet screen but not likely. I’m leaning towards replacing the electric fuel pump. It may not be putting out enough pressure. The pump is several years old. Does anyone have a suggestion for an Electric fuel pump? This one may be pretty tired.
 

PJL

Well-known member
The carb could be jetted wrong. It's been decades though since I fiddled with Webers. I see in the pics the open vacuum port on the carb. Is that supposed to connect to the distributor?
 
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Idaho IMP

Member
Thanks PJL. The pictures I’ve taken are somewhat out of sequence. yes, that port you’ve called out is for the vacuum advance. It has been connected. I’ll call Dan at Snowcat Service today. He supplied the new carb to the PO just before I picked it up. A larger jet may be the answer.
 

PJL

Well-known member
Could be a vacuum leak somewhere else too. Spray some carb cleaner or other flammable around the base and see if the engine speed increases.
 

Drifli

Active member
I ran the same carb on my IMP and it worked flawlessly out of the box. Thing would run perfect absolutely no issues. I’d look for air leaks as pointed out above, but also make sure you do a full tune up on your distributor.
 

Idaho IMP

Member
I ran the same carb on my IMP and it worked flawlessly out of the box. Thing would run perfect absolutely no issues. I’d look for air leaks as pointed out above, but also make sure you do a full tune up on your distributor.
Thanks. I’m fairly certain this machine has the original plug wires, cap and rotor. They’re crispy critters. I have a pile of tune up parts on the way. I’m going to start with a major tune, Pertronix conversion then go after the carb. bothe valve cover ports were capped off so I’ve gotta integrate that into the air intake. No wonder this thing is covered in oil!
Im curious how you ran your throttle linkage. Mine was easy To figure out but I’d like to see yours if you have a picture. I’m also going to remove inlet fuel screen and idle jet to look for a chunk of crap that may be restricting fuel.
Thanks for your response and advice.
 
I replaced my tired electric fuel pump with a facet pump from Napa Auto parts. My machine use to need choke all the time until I put a remote K&N filter on and now once warmed up no choke needed. The new facet pump is ethanol compliant and solid state. be sure and read the instructions and mount the pump at 45 degrees with the inlet below the outlet.
 
My JW had a paper filter on it that looked new but I suspect being outside all the time the paper swells up with moisture. The filter I put on is a Spectre, which is a copy of the other company. My new fuel pump is below the tank as apparently they are not self priming.
 

KickerM

Active member
Site Supporter
GOLD Site Supporter
I always mount my pumps below the tank even if they are self priming! Makes your pumps last much longer!
 

Idaho IMP

Member
Sorry it’s been a while since I’ve posted but I’ve finally had the IMP off the trailer! Turns out the “New” Weber ICH 34 was missing the plug over the progression port on the outside, hence the massive vacuum leak. I have sourced and installed the missing plug and it runs great! I have also cleaned/reinstalled the original Donaldson oil bath air filter under the driver’s dash board and properly connected all breather lines to the air intake, etc.
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Idaho IMP

Member
Hey gang,
Im in the process of replacing my two front seats in my 1404. The old ones are all but destroyed. The current seats are likely original and have adjustment tracks bolted to the bottom of the seats and the tracks bolt directly to the floor pan without any sort of riser. The seats are definitely wedged down where they sit between the engine cover and door frame. My rear seats have the same adjustment tracks however they sit on these nice riser brackets, about 3” tall. Can any of you Imp folks tell me if there should be that same riser for the front seats , or are the sets just meant to be slammed down to the pan? I have some extra head clearance to work with. I don’t have any pics yet but can get some later today. FWIW, my replacement sets are by Rugged Ridge. Meant for a 55-mid 70’s Jeep CJ. I got a pair for $300 bucks from my Jeep parts supplier. They look identical to the originals.
Id appreciate some feedback from other imp owners. I may borrow the rear seat brackets to mock things up. Thanks!
 

BoyToys

Active member
Ok so I’ve been here for a bit. I thought it was time to start an ongoing repair thread for IMP 669. This was the unit and matching trailer for sale during the holidays on KSL. The family and I did a 1200 mile round trip to pick it and it’s matching trailer up. We’re in Southern Idaho. The cat was in Northern California, northeast corner.
On the day of pickup, I had to swap out the old hubs on the trailer so I could use a set of 6 lug trailer wheels I had from my deck over trailer. The condition of the old 14.5” tires on the trailer was bad. They would not have made it 100 miles. I ordered a set of conversion hubs through R and P carriages that would fit the #42 spindles on the old axle. I pre-packed the bearings so all I would have to do is remove the center nut, and pull the old wheels off, Install the new 2-1/4“ inner seal, and bolt new hubs on. Piece of cake. I had both sides rebuilt and towable within an hour. The trailer lights were completely shot. I’ve never seen wire insulation turn to dust. Luckily, I had brought a pair of magnetic tow lights, so I slapped ’on after loading the cat.
Now for the good part. The Imp was about 6 miles down the road, and 4 miles up his access road, dead. He hadn’t had the chance to install the new carb or alternator. Sooo, I towed the trailer up the road to the cat. Oh yea, there was a solid foot of snow on the road. Parts of the road was over 10% grade, so we had that going for us. Luckily there was a wye in the road where I could get turned around, to load the cat. I brought a 4000# come-a-long and a bunch of rigging goodies to load the cat. We drug the cat down backwards with a recovery rope. I then backed the trailer right up to the cat, tilted it down, rigged up the come along, and proceeded to yank the imp onto the trailer. It wasn’t easy, but I got loaded. by now it was getting close to dusk, so we headed out back towards Burns, Oregon. The trailer did great, it towed like a dream. We made it back to home the following day without incident.
Nice to know I'm not the only one with a single axle Thiokol trailer, but seemed to work fine hauling my Imp for a couple hundred mile trip over Snoqualmie Pass in August. Well....worked fine other than one wheel bearing turned out to be toasted not 50 miles into the drive. Wheel was wobbling, getting hot, but I just kept going white knuckling all the way.
Made it home, grabbed a beer and laser IR thermometer, and recorded 260°F hub temperature. Needless to say it was smoking....litterally.
 

Idaho IMP

Member
Yikes, that’s a bummer! thank goodness you were able to make it home. While my axle is still serviceable, I just took delivery on a new 5200#, heavy 3” tube axle nev’r adjust brakes, and ex lube spindles. I haven’t swapped it out yet, but hopefully soon.
Im surprised how heavy the combo of Imp and trailer tow. It’s quite a bit of tongue weight. I can’t imagine towing with a sub Half ton pickup. My P.O. Told me he towed the rig behind his Rav-4!!
I’d have to think your spindle is shot given the wobble and heat on the drive home. Keep us posted once you tear into it.
 

BoyToys

Active member
Yikes, that’s a bummer! thank goodness you were able to make it home. While my axle is still serviceable, I just took delivery on a new 5200#, heavy 3” tube axle nev’r adjust brakes, and ex lube spindles. I haven’t swapped it out yet, but hopefully soon.
Im surprised how heavy the combo of Imp and trailer tow. It’s quite a bit of tongue weight. I can’t imagine towing with a sub Half ton pickup. My P.O. Told me he towed the rig behind his Rav-4!!
I’d have to think your spindle is shot given the wobble and heat on the drive home. Keep us posted once you tear into it.
Yeah I would suspect the spindle is toasted but won't know until I get in there. Replacement parts I can only hope to find. Right now focused on the cat.
I towed it with my Toyota Tacoma. A couple long steep grades had me maxed out at 40 mph but otherwise did OK. The trailer is not light weight, and the Imp itself I think is around 2600 lbs., plus maybe another 150 or so for the blade and hydraulics.
 
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