plsmoothy

Here's the rub guys. My landlord is a rich kid who let a 1993 RX7 sit for over 7 years in our parking lot here in Los Angeles. He has asked me to try and start it after all of these years. It is a twin turbo which he has been modified to some degree. I don't know the mileage on the car because I haven't connected a battery to it yet. By the way I have already informed him that there is a good chance that the apex seals are carbon locked beyond repair and it is more likely than not that this car will not start.

Here are the mods to the best of the owners recollection: Turbos polished, catalytic removed and custom exhaust installed, ECM modified or possibly replaced to deliver more power, and I believe he said the fuel injectors were replaced or modified to deliver more fuel.

I've done my due diligence and read many threads on starting a rotary engine that has been sitting for a long time and I'm ready to begin this job. Today I'm going to remove the leading plugs and add either Marvel Mystery Oil or Seafoam and let it sit for a couple of days.

I have the following questions. Does one of these work better than the other? Also, approximately how much should I introduce into the combustion chamber? I appreciate your responses in advance and feel free to include any other advice or pertinent info. I'm sure this will be the first of many posts so I'm looking forward to getting to know this community.

Best

firecaddie

WondrousBread

If I read your post correctly, you want to introduce Seafoam to the combustion chamber before start up to loosen the carbon?

Seafoam is very effective for cleaning the fuel system (as stated above) and also removes carbon from the combustion chamber (though how effective it is has been debated) when added to fuel. However, I wouldn't add it to the combustion chamber before a start up only because it doesn't have any lubricating properties like MMO does.

Have you tried turning the motor by hand? You should be able to slowly rotate it by hand in neutral, and if you don't encounter any problems you don't have carbon lock. It probably has some carbon, but if it isn't locked at least you can try to start it. If facing the engine from the front, the direction to turn the crank pulley is clockwise. I think you can do it using a wrench on the alternator bolt, but I've never had trouble doing it with just bare hands.

I'd also expect after sitting so long that you will need to replace the fuel, all filters and fluids, and almost certainly have the injectors serviced and the vacuum and fuel hoses inspected (if not replaced).

plsmoothy

Thanks for getting back to me WondrousBread. Just finished working on the rx7 for day and here's the status.

Yesterday I removed the plugs and added about 4 ounces of Marvel Mystery Oil to both combustion chambers. Today I removed the accessory belts so I could turn the engine directly from the crank pulley. Much to my surprise it rotated rather easily. Correct me if I'm wrong but I feel like thats a good sign considering those rotors haven't moved in 7 years.

Tomorrow I'm going to check the compression in the chamber. I've watched a couple of Youtube videos where guys use the standard compression gauge that one would use for a piston engine. Any thoughts on this? I'm going to disconnect the fuel injector fuse so the old fuel doesn't flow the system. I was also going to add a little oil to the chamber. Any and all advice is greatly appreciated.

plsmoothy

Hi firecaddie. Please tell me how you went about in flushing the fuel system.

WondrousBread

The fact that the engine turned is a good sign. An engine carbon locking in place is not super common, but what is common is the seals sticking in place with carbon. The engine will still turn over, but there will be lower compression (this can be deceptive, read on). The way the apex seal is pressed against the rotor housing is through use of a spring that rides under the apex seal in the groove in the rotor. If the spring and seal hasn't moved for years, the carbon can glue it in so that when it is moved, the spring can't push the seal outwards to seal against the housing. This means lower compression on two faces of the rotor. This is part of the benefit of the MMO. MMO has both lubricating and solvent properties. It dissolves carbon, but also lubricates the chamber so that if/when you start it, you aren't starting it dry. In addition, the extra lubricant helps sealing, making it easier for the engine to compress and start (especially after years of sitting).

You can use a piston compression tester, but you have to remove a particular part of the valve. It's been awhile since I've done it but the procedure is well documented online. As I said above, stuck seals can make the result deceptive. Just because the compression appears to be low doesn't mean that something has gone horribly wrong inside.

How you want to proceed after that with actually starting the engine depends on how much your landlord is willing to spend. New plugs will make it easier. I recommend following the guide here: Removing An RX-7 From Storage, Dealing With Improper Storage
Aaron Cake wrote this a few years ago. Most of his material is focused on the 2nd Generation Rx7, but the principles are the same for 3rd Generation Rx7s such as yours.

When I purchased mine, the previous owner had let it sit for over 3 years in his garage without starting. As I was mostly concerned about getting it home, I didn't check much of anything other than that it ran and didn't overheat. Turns out down the road the radiator was low, and the alternator belt snapped meaning I had to stop and jump it 12 times on the long drive back home. Obviously your situation is a bit different, but if your landlord's budget allows for it I suggest replacing the fluids, belts, hoses, and flushing the fuel system ahead of time. Dealing with the problems before they appear is important. For more information specific to your landlord's car, I suggest reading the FAQ section for 3rd Generation Rx7s and selecting the links you need: 3rd Gen FAQ

Good luck, and keep us posted on the results. It will be good to see another Rx7 put back on the road

plsmoothy

Thanks for all the info guys I greatly appreciate it.

Currently I'm trying to remove the UIM and having a heck of time. I searched the forum for a write up on how to do this but the links to the write ups are not working. Can anyone steer me in the right direction?

SpinningDorito

iTrader: (2)

This write up is helpful: https://robrobinette.com/manifold.htm

There are also several good videos on youtube if you google "rx7 fd remove UIM"

plsmoothy

Thank you for that. With the aid of a youtube video i was able to get the manifold off.

On to my next issue. The fuel injectors on this car have been sitting for at least 7 years and i'm sure they need servicing. Does anyone know of a good write up detailing how to remove the fuel injectors. It is more than a little daunting considering they're located under the rats nest and ignition coil pack. Any and all suggestions are welcome.

SpinningDorito

iTrader: (2)

This is the writeup I just used to remove mine this weekend (https://www.rx7club.com/3rd-gen-arch...cement-232603/)

The primary and secondary rails are next to each other between the rats nest and the air control valve. The most straightforward way of removing them is to take the ACV and the rats nest off first.

There may be tricks to getting to the injectors without removing the rats nest (I believe there are some phillips screws you can remove and then pivot the nest out of the way) but honestly, if you're going to pull the fuel injectors out, it wouldn't be unwise to service the rats nest and do a vacuum line job, replace the old fuel lines, etc. If those lines are original you're pretty likely to break some of them trying to avoid taking the rack out anyways.

I'm currently going through this process, and when I look at my old brittle lines the wrong way, they just fall apart.

Sgtblue

iTrader: (16)