I recently purchased a 1990 13b rx7. They guy told me it had some fuel system problems, so i was just gonna do a pump and filter and so on. Yet after many attempts to get it crank over even slightly nothing happened. The motor turns and spins freely and has spark. So i was then advised to do a compression test. So I did, i removed all plug wires and took out both my leading plugs. Then i tested each cylinder to come back with about 75PSI. From what i have read i believe for it to be a motor in good shape it should have 90+PSI. The guy i got it from supposedly had a motor rebuild 45K ago, then let it sit for about a year or so. So i am stuck on what to do now, could the apex seals have shrunk or seized. Is there any way to fix this problem? Any help is much appreciated, thank you.

 

does it "roll over" with the Key?
or is it Cranking but will not start?

You are saying you can't get it to crank but the engine moves freely...

(dont say Cylinder..it's a Rotor housing!)

 

It does roll over with the key, like its not seized. The rotor moves freely. It will just not start as in fire and run.

 

rule #1 when buying a used car, take whatever the owner your buying it from, and take it with a grain of salt.

stop throwing money at it and compression test it, if its sat for a year, and it was "rebuilt" 45k ago, I would be leary

Borrow compression tester and test it

Is My Engine Blown?

 

I already did a compression test it has 75psi

 

Overall? Or 3 even bounces on both rotors?

 

I believe it was 3 even bounces

 

How have you addressed the "fuel system problem."

 

I have not addressed it yet, I mean I thought before spending more money in it the compression would be more important, to make sure it would have a sufficient amount.

 

The easiest thing to do is to jumper the fuel check connector and see if the car then starts. You can also disconnect the return fuel hose and place it in a jug. Then jumper the fuel check connector and w/key to on the jug ought to fill up rather quickly. You could also borrow a fuel pressure gauge from an auto parts store and place it in line w/either fuel hose (send or return line) and w/key to start it should read close to 35 psi (check the FSM for the exact reading).

 

But shouldn't I address the engine compression first?

 

Depends on if 75 was overall or bounces, you said you weren't quite sure. 75 is low, but being a N/A, it should run, mine has 70psi on the front rotor and fires everytime, but every engine is different depending on damge internally

I'd say compression test it again and be sure your at 75psi BOUNCE wise, if your above 75, than worry about fuel delivery and follow what satch said, when it comes to anything electrical on these cars, he's the man, i literally think he has the FSM electrical section memorized lol

 

So then if it has compression of 75, bounce wise, it is okay? what about all this adding oil in the plug holes to build compression?

 

Thats mainly only to help a flooded engine start, it will build compression, but as soon as it fires it will burn it off

 

75psi in the rear or front ? What was the compression
On the other housing ?

 

So after trying a few things it fired over. But only for about 4 seconds and with help of starter fluid. It then revvs to 4 grand and dies, what should i do now. I have replaced the fuel filter and the gas is getting to where it connects to the intake. I just dont know where to go from here, could it be injectors or just a clog???

 

Now that the engine compression issue is solve... I would address whatever is related to the fuel(if you believe what the guy said) look it up in the Haynes , it's pretty straight forward , a multimeter is a great cheap tool

 

I like post #10 but I'm somewhat biased.

 

Where is the fuel check connector and how do I jump it? Am I just looking for fuel flow then?

 

It is located between the passenger strut tower and the motor. It's encased in a black rubber boot and inside should be a Yellow plug w/two wires. One wire is Black while the other is Brown. It's part of the emission harness so it comes off the harness which feeds the boost sensor. W/key to on it causes the fuel pump to turn on. Once the car starts your ECU keeps the pump running. If the ECU is not supplying the proper signal the engine would die. By jumpering the fuel check connector it will make sure that the engine continues to receive fuel.

 

So then if it doesn't start it's the pump and if it does its a bad Ecu?

 

It depends.

 

So I did a fuel pressure test, and it's 40psi. So that's all good. I guess I have a clog somewhere in the intake?

 

If you disconnected the Wires to the Air Flow Meter (at the airbox/filter) then the car will just start and die.
IF you introduced "quick start" after the air box then most likely the hose is OFF to the airbox and the AFM is not seeing air at all.
In this case the car again will just start and die.

 

Excellent deduction watson, that never crossed my mind