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-   -   Compression, spark, fuel, air, what else? (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/compression-spark-fuel-air-what-else-1036275/)

slitherz90gxl 05-25-13 09:22 PM

Compression, spark, fuel, air, what else?
 
I made a thread last week about this but abandoned it after the car in question caught on fire. However, I ended up cleaning everything up and decided it wasn't as bad as I had thought. I'm currently waiting on block-off plates and creating a wiring harness for it.

I have 90psi on all six faces and have a video I'm going to attempt to attach so I can make sure that it is right. It does the same thing for the front and rear; I think video is of the front.

I am getting spark,fuel, and air. The fuel pressure checks out as well.
It has everything it needs to start but it chooses not to because rotary.
Any suggestions?
Am I misreading my compression test and it is actually blown?

slitherz90gxl 05-25-13 09:28 PM

025 - YouTube

slitherz90gxl 05-25-13 10:18 PM

025 - YouTube

I have no idea why it posted twice. It even told me it didn't post at all because I was logged in. sorry.

Nick_d_TII 05-25-13 10:45 PM

Timing. Can set it to TDC and check/restab the CAS...

https://www.rx7club.com/2nd-generati...ng-cas-427031/

https://www.rx7club.com/2nd-generati...estion-646857/

Be sure it isn't flooded either...

slitherz90gxl 05-25-13 11:06 PM

I tried that and will try it again whenever I get everything put back together.
The car was running great and then just died on my way to work. I was running around 2,000rpm, just cruising through town.
So I'm leaning towards an electrical problem but since it has all the essentials I'm not sure. Unless the ECU went bad and is messing with the injector timing.

korndog517 05-26-13 01:32 AM

Check all grounds, especially the engine ground. How did you verify you have spark and fuel?

slitherz90gxl 05-26-13 01:41 AM

I held a screwdriver to each spark plug, one at a time, and watched it ark. I also pulled the primary fuel rail off and watched the injectors fire.

korndog517 05-26-13 02:30 AM

well, just because you see a spark from a screw driver and fuel comming out of injectors doesnt mean that you have correct fuel and spark....

need fuel pressure readings, and actually use a real spark tester. also check for carbon tracking on the plugs. when was the last time the plugs and wires were changed?

slitherz90gxl 05-26-13 09:48 AM

I checked the fuel pressure and replaced the plugs and wires. I have no idea where to get a "real spark tester". I know if it is a bright blue spark it is probably more than enough to ignite. Also that engine fire I had was a pretty good sign I'm getting both.

RotaryEvolution 05-26-13 12:26 PM

i thought you cured the problem which was a bad ground connection on the block.

now the reason it caught on fire is another issue, which means it had to be leaking fuel from the injectors or lines and have an ignition source like a faulty plug wire.

slitherz90gxl 05-26-13 03:39 PM


Originally Posted by RotaryEvolution (Post 11478184)
i thought you cured the problem which was a bad ground connection on the block.

now the reason it caught on fire is another issue, which means it had to be leaking fuel from the injectors or lines and have an ignition source like a faulty plug wire.

I don't think the ground is what was causing it. It is doing the exact same thing and I have double checked everything. The fire was my fault. I didn't have a hose clamp on all the way and the fuel was leaking right above the spark plugs. That is what I get for being in a rush.

So did that compression test look alright? I mean, 90psi is low but it isn't low enough for it not to start, right?

jjwalker 05-26-13 07:17 PM

90 is low, but totally driveable. My last motor was still running fine in the 60-70's range. No damage, it was just wore the hell out (159k miles original engine).

slitherz90gxl 05-26-13 10:09 PM


Originally Posted by jjwalker (Post 11478464)
90 is low, but totally driveable. My last motor was still running fine in the 60-70's range. No damage, it was just wore the hell out (159k miles original engine).

Yeah, my first rx7 had 90's all around on the front and 60's on the rear. It ran for two years like that. I don't know. I'm hoping that it was just a vac. leak and blocking everything off will work. I can deal with it not starting in cold weather, it is the summer and a vert. I'll just park it in the winter.

RotaryEvolution 05-26-13 10:16 PM

it should start yes, and it sounds like it is. but the reason it is shutting off is the problem which could be any of a number of things:

vacuum leaks cause the afm door to close and shut off the fuel pump after initial crank, resulting in a 2-3 second start and stall.

low idle speed settings with the cold start assist solenoid bumping up idle temporarily during crank can result in a start and stall condition. (could be diagnosed by applying throttle and it should stay running)

erratic injector function results in start and stall as the engine struggles to run on one rotor.

low fuel pressure/volume used up by initial startup can result in a start and stall condition.

a faulty ignition switch will shut off the engine as soon as it returns to the run position from crank position, where the bad contact point is.



those are just a few common issues i see with FCs.

slitherz90gxl 05-27-13 02:33 PM


Originally Posted by RotaryEvolution (Post 11478601)
it should start yes, and it sounds like it is. but the reason it is shutting off is the problem which could be any of a number of things:

vacuum leaks cause the afm door to close and shut off the fuel pump after initial crank, resulting in a 2-3 second start and stall.

low idle speed settings with the cold start assist solenoid bumping up idle temporarily during crank can result in a start and stall condition. (could be diagnosed by applying throttle and it should stay running)

erratic injector function results in start and stall as the engine struggles to run on one rotor.

low fuel pressure/volume used up by initial startup can result in a start and stall condition.

a faulty ignition switch will shut off the engine as soon as it returns to the run position from crank position, where the bad contact point is.



those are just a few common issues i see with FCs.

Thanks. I'm going to check most of these things today. I'm going over my wiring to make sure everything is right. I was actually considering a problem with the ignition switch because of some weird occurrences last night. It might have been nothing. My check engine light stayed on with the key in the accessory position. Also the Gear selection lights on the dash were lit up; not all of them but just the one I was in. (P) or (N). It also won't start sometimes unless I have the transmission in Neutral. It just clicks in park.

I'm not sure if these are related or not because I've not messed with an auto rx7 but I'm reading through the FSM as I type.


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