RX7_21

Hi, just finish fixing the hose today and it seems that the compression of the engine is too low, i'm still wandering what's wrong with it as the previous owner of the FD was telling me that once i fix that hose, the car will be up and running. what should i do?

RX7_21

To be more exact, i just fixed the radiator cap, fuel evaporative system, i just installed a new fuel line from catch tank and the wiring from the purge valve is ok. This is all the parts that i need to fix and this is the info that i got from the previous owner. But after i fix all this, i still can't start the car, i just change a new battery too.

RX7_21

Any advise or assistance would be much appreciated. Thanks in advance.

RotorJoe

What do you mean by the compression being low? Have you had a rotary shop test the engines compression? Or does it just not sound like it gets compression to start the engine?

Also have you had a coolant system pressure test done? This can be done by you if you have a pressure tester (different for engine compression tester)?

XSTransAm

you bought a rx7 without hearing it run and thought it had a working engine?

RX7_21

Sorry for giving a vague description. It does not sound like it gets enough compression to start the engine. I don't think there's anything wrong with the coolant system though, i just checked it ust now. How much is it if i want to buy the pressure tester?

sorry for being such a noob...but i'm still learning.

RX7_21

Actually when i bought it from teh previous owner, the car does not work at all, but i was thinking it's ok since i want to learn how to fix it by myself. anyway he told me the current existing problem that he think that need to be fix, which is mentioned above. So i've been fixing it for 2 weeks and when it finally been fixed, i still can't even start the engine.

XSTransAm

well you need 3 things to start an engine, compression, fuel and spark.... verify you have all three.

fuel can be tested simply by smelling the exhaust after cranking

spark can be verified easily with a timing gun or by holding the spark plug to a ground while cranking.

compression is the hardest to check, but you should be able to get an idea with a 25$ tester from any local auto parts store. read up on compression testing procedures and see whats going on... if your really uncertain you can always take it to a mazda dealership and pay the 75-100$ to have them check it.

Mike

RX7_21

erm..mazda dealership?
i don't really trust the skills, heard lots of things about them. But i do order some parts from malloy mazda though, their price is really affordable. I'll get the compression tester tomorrow, is autozone selling it?

I can borrow the timing gun from a friend of mine, i can smell the fuel from the exhaust when i try to start the car.

Thanks for the help bro!

i'll update you again for the outcome tomorrow.

rx7dreams

iTrader: (1)

I'm a newb myself, but I was just thinking, can't an engine with low compression be caused by a bad starter, high resistance in the starter circuit, or just a slow turning starter even though the battery is good? After reading all the replies, I notice that the starter wasn't mentioned.

I could be wrong and I'm always trying to learn.

RX7_21

hm...so far from the shape of the starter when i look at it, it seems to be in ok condition, maybe you're right, i'll go and check it out tomorrow first thing in the morning. Thanks for giving me advise.

XSTransAm

if the car is cranking at a reasonable speed then the starter is not the problem.

It is also possible that the car is flooded...

after you compression check it i would head down that route. if you search you can find plenty of info on unflooding procedures.

Mahjik

iTrader: (1)

RX7_21,

Have you had a compression test done on it yet (before or since you bought it)? It really sounds like you've got a bum engine on your hands.

XSTransAm

also the mazduh dealer is "usually" capable of doing a compression test, just dont let them do anything else

wrankin

Well, it really sounds like the engine is flooded. Considering that you were having fuel problems, this is very possible. Do you have a heavy gas smell from the exhaust?

Remember flooded == low compression.

Also, a compression check is of limited use if the engine is not warmed up when you do it.

Mahjik

iTrader: (1)

That's not entirely true. While it will give you different readings (hot verses cold engine), you can at least make sure all the readings are close for each face regardless of the engine temp.

RX7_21

I have not had any compression test and the gas is not really heavy, just do the compression test of the car, the purge valve is ok the oil coolant is fine, here's the result for the compression test: .0 kgf/cm2 or 100 psi minimum @ 250 rpm. Well since this is my first time doing the compression test, i might not be accurate. So what did you guys think?

XSTransAm

here are vids of me doing the compression on my blown motor... if yours looks like this its bad :P

https://www.rx7club.com/showthread.p...hreadid=308325

RX7_21

bro the link does not work.

1QWIK7

iTrader: (33)

the link works dude, the vid files are inside the link..

RX7_21

damn....that's the **** i'm experiencing right now.

XSTransAm

how long ago did you buy the car? and how much did you pay.

you may still be covered under the lemon law and he could be required to give you your money back... if the engine is blown the car isnt worth a penny over 8k. (if its immaculate)

do you see 0 compression? i think my rear rotor might have been ok as i have not heard back from the rebuilder yet. but my front with no compression was gone.

If your uncertain you should have a mazda dealer do the check, they can give you a definitive answer.

RX7_21

no, is not 0. Mine is somewhere like 7.0 kgf/cm2<--it might be lower or 100 psi minimum @ 250 rpm, is that good?

i don't even know how to read that thing.

XSTransAm

you should be getting three bounces of the needle. you have to hold the valve open while you crank the engine so that you can see the difference between the three rotors. and your not gonna get 100psi on a cold engine.

RX7_21

I must doing it the wrong thing then. Let me go and check now and i'll update you.