After seeing the fuel blow back through the carburetor, it is time to remove the cylinder head and see what is up with cylinder 3. I removed the valve cover, intake manifold, exhaust manifold, and various other external engine parts till I could remove the head.
Well not ideal but at least the pistons don’t have holes and no foreign objects in the cylinders.
The cylinder head is coated in oil and corrosion.
Here is a close up of the intake valve on cylinder 3. Seeing some crusty rust.
Rest of the parts for the engine. Going to ultrasonic clean all these (minus the carb I just rebuilt) before reassembly.
Tearing down the cylinder head more. So far everything looks ok. Cam, tappets, and surfaces look nice and not abused.
I cleaned up the surface of the head and removed the intake valve of cylinder 3 to make sure this is repairable.
The valve is stainless so this rust is just deposits, should clean up with a brass wire brush. The intake port is rough. I won’t know if the seat is salvageable till I get the surface rust off.
Here is the rest of the internal parts after cleaning through the ultrasonic cleaner and a brass wire brush on the valves to clean them up.
The cylinder head didn’t exactly fully fit in the ultrasonic cleaner but we will make this work.
Ok before we get into the carburetor rebuild I did manage to get the engine to run on 3 cylinders. I popped off the top of the carb so I could manually fill the gas bowls.
The engine does run but it is not happy at all. There is a back pressure through the carburetor. I suspect that cylinder 3’s intake valve is rusted up and not closing. This explains the zero compression as well. You can see the back pressure blowing gas upwards out of the carb and how much blowby the engine has. Oil is got everywhere!
The Jeep came with a 2 rebuild kits and a parts carburetor so getting at least one functioning carburetor should be doable!
The carburetor is a Holly 5210 which is Holley’s version of the Weber 32/36. It even says Weber inside the bowl. This page has a good break down of how the carburetor comes apart and is reassembled.
Above is the diagrams from the carburetor rebuild kit and the diagram from the DJ-5G service manual.
I disassembled the carburetor and organized the parts for it.
Ooo that fuel bowl is crusty. I put all the parts in my ultrasonic cleaner with a parts cleaner solution overnight.
After some careful cleaning with some carb cleaner and scrubbing the stuff the ultrasonic cleaner didn’t remove we have a pretty clean carburetor. The jets I hit with a brass wire brush to really get the crust off.
All back together. I am missing one of the air cleaner studs so I will have to pick up a spare bolt from the hardware store.
First thing, easy way to see if the engine runs. Throw some ether starting fluid into the carburetor, turn the key, and then crack some beers cause the engine is running. Well that isn’t what happened.
The starter clicked but the engine didn’t turn over. It was locked up. I pulled the plugs and put down a bore scope.
Well that is not good.
Remember this is an AMC 121 engine that is basically a Audi EA831. This block is aluminum silicon. The head is aluminum. Where did all this rust in the cylinders come from? This is cylinder 3. Looking on the porsche 924 forums, the head of this engine has stainless valves but steel valve seats. That is where the rust has to have come from. So we are dealing with rusty intake valves but the engine is frozen.
Over a couple days I soaked all the pistons in a mixture of ATF, acetone, and brake fluid. This mixture really creeps and loosens stuff up. I just poured it down the sparkplug holes. After a couple days of hitting the starter it finally broke free and started spinning.
We got an engine that spins! With the plugs out lets test the compression.
110lbs
90lbs
0
90lbs
So uh, cylinder 3 with all that rust is not happy at all. We either have a bad head gasket, valves are trashed, or rings are cracked. That engine head has to come off to properly check and fix the problem.
Lets see if we can get the engine to actually run before tearing it apart though. The carburetor needs to be rebuilt and the Jeep came with 2 rebuild kits and a spare carburetor for parts.
This is my “new” 1979 DJ-5G Dispatcher Jeep. I picked it up near the end of May.
Posing with the “kill” :) Yes its painted with zebra stripes…. or what is left of the stripes.
Once I got it home I put it up on jack stands and started to really dig into what it this Jeep is.
This is a “G” model of the Dispatcher, which was a really short lived variant. The big difference between this Dispatcher and other models was it has the AMC 121 2.0L i4 engine.
This is a very interesting engine and the history behind how these ended up in AMC vehicles… and the Dispatcher Jeep!
The EA831 engine, also known as the “Audi EA831,” was developed in the late 1960s. During the late 1960s, Audi sought Porsche’s engineering expertise to develop a new range of engines. Porsche, which had a strong reputation for engineering and performance, worked on several projects for Volkswagen since the 40’s, including the EA831 engine.
In the early 1970s, AMC was seeking to modernize its engine lineup to stay competitive in the automotive market. They had the small, light weight compacts that the gas crisis needed but not the engines.
In 1973, AMC struck a deal with Audi (then a part of Volkswagen Group) to use and license the EA831 engine. This engine was adapted for use in the AMC Gremlin, Hornet, and later the AMC Spirit. As part of this agreement, AMC was not to use the VW or Audi names when referring to the engine.
They also changed how the engine was run, Porsche was pushing fuel injection but AMC did not want that added complexity nor could burden the costs of developing a system. Thus, AMC went with a 2 barrel carburetor with a traditional points distributor. This is what became the AMC 121 engine.
Audi and Volkswagen ended up not using this engine, it was in the Audi 100 and the Volkswagen LT van. Porsche on the other hand had to pick up the pieces of the 924 fall out with Volkswagen and kept this engine there.
Basically if I need to get parts for the engine. Porsche 924 parts work and fit!
Back to the DJ-5G. AMC used it in a couple vehicles like the Sprint but it ended up being in a weird price point. The overhead cam engine was more expensive then the larger straight six and four engines that AMC was using at time. The engine was more fuel efficient then the old push rod designs but the extra price put it in the bracket of the V8 powered options. Economy at the time (and still now i suppose) was cheap = fuel efficient and expensive = powerful. So an expensive inline 4 that got good gas mileage occupied a weird spot in the market.
AMC used it in the Dispatcher jeeps but did not use the engine for long. Once AMC could get out of the deal they did. The post office also didn’t really like the small inline. You really had to rev the engine to get torque and drivers would just red line it all the time.
My copy of the DJ-5G is in ok shape. Frame is solid and the majority of the body is clean for its age. It does have one bad rust spot that will have to be fixed.
The drip rail here is rusted through which compromised the seam sealer. This ended up rusting out the upper roof frame.
This will need to be addressed but the first call to action is to get the Jeep driving again.
