The Spyder

iTrader: (8)

A while back I rebuilt a friends of mine 89 S5 NA due to bad oil control rings. Easy rebuild, everything cleaned up nicely, everything spec;d out. Started first crank on reinstall. With 1000 miles on the engine, he is still having bad hot start issues. The car has to cool at least 30 mintutes before it will even think about starting again. Lots of unburnt fuel/ rich when running, no power.

Checked compression cold, no throttle open. (Crappy tester)
90-90-90
85-90-92

Good enough numbers.

I noticed his Fuel Pump resistor pack was making a awful clicking noise. Tested it tonight, it was way out of spec. Replaced it with a decent used one and its still having issues. He had a SAFC installed, I double checked everything, everything is fine. Re setup the SAFC for his S5, nothing. I tested every sensor except the Coolant Temp on the backside of the water pump housing. (Im about to go check the voltage drop at the ECU since I dont have time to yank the manifold.) We are ordering a new one tomorrow. I have a feeling that its the problem + weak optima battery that cant spin the motor fast enough. (Very sluggish cranking.)

I will report back tomorrow, but this is a PITA.

Anyways, my question is his AFM is making a audible clicking noise when cranking, you can feel it in the body of the AFM. Whats causing this?

mazdaracer78

never heard an afm click...

i've heard injectors click when they register...

have you tested the injectors for leakage? it sounds like an injector situation to me.

Derekcat

iTrader: (8)

I still have that AFM that I grabbed for that guy you referred to me.. He never came for it. >_<

Do S4/5 use the compatible AFMs? Want to try it?

mazdaracer78

s4 and s5 afm's are not interchangeable...

juan0

one factor may be your battery... since you can't get the motor to spin fast enough then it's just gonna pour fuel into the chambers maybe ignite... but it won't start... get a good size battery! not those fucken civic batteries... get one that fits nice and tight on the battery tray.. that's the size you should always use.., test your alternator for free at kraign or autozone..., then, get a fully charged battery.. and try to start it... with that done let me know what you find out about that temp sensor.. because i'm having the same problem... rebuilt engine.. just replaced coolant seals and then same symptoms you're having.. but mine is a little hard to start even when cold, i have to crank it, turn off the fuel pump, carnk it, wait for it to start and turn on the fuel pump again... i ahve to idle it at 1500 because any lower and it idles really bad.. the engine shakes like a matraka..., so ya let me know plz

meximan

iTrader: (37)

Im looking at a car with teh same problems. hoping to see what u guys dig up.!

dyoungre

As a test, shut the car off hot by pulling the fuel pump fuse.
Remove the key, and THEN put the fuse back in.
Let the car sit a normal amount of time.
Try restarting the car by turning the key directly to crank (don't sit on key on / engine off for any duration of time).

If it starts fine, then yes, it is the injectors. I actually had an '87 that was rigged with a fuel pump relay switch next to my seat. I'd kill the engine with the fuel pump switch, and then never had a hot restart problem again - lazy fix to leaky injectors !!!

jackhild59

iTrader: (7)

Slow cranking can be the entire problem. I had an optima yellowtop in my car. As it got old, the cranking slowed down. If I had any hicup-the car became difficult to start. This after 20k miles of goodness, easy start every time. A new, hot battery fixed the problem. Its worth a try. Maybe cheap fix

Regarding the no power issue- I don't think you have a clue about the compression, since everything you listed was wrong, throttle closed and cold Also, unless you used a Mazda compression tester or an electronic graphing tester, http://rotarydiagnostics.com/ how did you diagnose those precise pressures on each face? Seriously, you cannot get numbers like that with a 'crappy' piston type tester.

I hope you were more careful with the rebuild than you are with your diagnosis. Not bashing-you may have done a superb job on the rebuild. If you did, do a better compression test to verify compression is good.

Did you have the injectors rebuilt? Leaky dirty injectors could contribute to the the hot restart and the power issue.

Good Luck!

jackhild59

iTrader: (7)

You should buy that car.

meximan

iTrader: (37)

ALot of people use the regular compression testers. sure its not precise on the reading but people dont have the serious cash to invest in a mazda compression tester. Atleast you can get a a pretty good estimate with a normal one.Spyders pretty good with rx-7's, hes a local up here-doubt that he doesnt know what he is doing. Spyder whats the news?

jackhild59

iTrader: (7)

Yes, you can. I use one myself.

http://www.youtube.com/watch?v=RqwXM...e=channel_page

I also wrote this:

https://www.rx7club.com/showpost.php...65&postcount=3

Yes, you can get a pretty good idea of the integrity of the apex seals with the bounce test.

You can get a pretty good idea of the max compression of each rotor with the compression test.

Neither one can tell you what the compression is on each face, like Spyder posted.

All I am saying is if he wants help diagnosing the problem, he needs accurate information. The test results he gave are not possible with his claimed method. Something is missing. It might be his communication style, or he might be making some assumptions or he might have some additional information that he hasn't shared.

I'm just saying...
Edit:

I also believe that a new battery and cleaned injectors will likely fix the problem.

meximan

iTrader: (37)

cool vid!