New Rebuild Starting Issues
09-28-2003, 04:57 AM
#22
Senior Member
Join Date: Jan 2003
Location: Perth, Western Australia
Posts: 267
Sounds like low compression due to apex seals or side/corner seal clearance being too great.
My first ever rebuild was the same- pull started really easily but couldn't start on the key. Mind you, I was using second hand seals that I had scrounged out of a couple of dead motors and didn't have a clue what I was doing back then (and some would argue I still don't...
)
It could be a huge vacuum leak somewhere, I guess that would be the first place to look. If it's still no good, there is a fairly radical measure you can take, which is to put some bon-ami (Ajax or Jif?) powder down the inlets which forms an abrasive paste and beds the seals in very quickly. This used to be a Mazda recommended procedure and bon-ami actually had a Mazda part number!
You know the powder I mean? Household cleaner used for cleaning sinks etc.
It might well be this that's the problem but if it's too great clearance on corner to side seals, you'll have to rip the engine apart and re-clearance them. They always have to be clearanced when new. Did you do this?
Also, what condition were the rotor housings in? If they're not perfect it can take some time for the apex seals to bed in.
750 idle is about right. It will hold idle ok even if the compression is too low to start on the key...
My first ever rebuild was the same- pull started really easily but couldn't start on the key. Mind you, I was using second hand seals that I had scrounged out of a couple of dead motors and didn't have a clue what I was doing back then (and some would argue I still don't...
It could be a huge vacuum leak somewhere, I guess that would be the first place to look. If it's still no good, there is a fairly radical measure you can take, which is to put some bon-ami (Ajax or Jif?) powder down the inlets which forms an abrasive paste and beds the seals in very quickly. This used to be a Mazda recommended procedure and bon-ami actually had a Mazda part number!
You know the powder I mean? Household cleaner used for cleaning sinks etc.
It might well be this that's the problem but if it's too great clearance on corner to side seals, you'll have to rip the engine apart and re-clearance them. They always have to be clearanced when new. Did you do this?
Also, what condition were the rotor housings in? If they're not perfect it can take some time for the apex seals to bed in.
750 idle is about right. It will hold idle ok even if the compression is too low to start on the key...
09-28-2003, 12:56 PM
#23
Senior Member
Thread Starter
Join Date: Aug 2003
Posts: 157
Well my dad went out there and started it this morning, and he said it started by key but didn't want to idle. Strange it starts when cold, but not hot eh?
Hmmm I don't guess we clearanced the seals that well. I used all new seals in the engine. We ground the seals down to make them fit in the rotor, as the manual said. We tried to get them as close to perfect as possible, but I think we went over a bit too far on one or two of them. I also had to use one old seal, because I broke one of the new ones sanding it down. The front rotor was kind of screwed up though, because it was carbon locked in the housing and no matter what we couldn't get it out. So we had to take the front half of the engine apart backwards(front housing first), and then once we got it apart, we had to beat the rotor out of the housing because we couldn't push it out. The engine had been sitting for something like 7 years I figure, though it only had 60k miles on it. I was amazed by the amount of carbon in it. Anyway I think that the seals might be sticking where we hit the rotor because those were kinda tough to get in. We had to sand down the bit where corner seal goes in to get it in, and it still didn't feel as smooth as the other rotor.
I suppose the next thing would be to check for vacuum leaks. I need a gauge or something I guess.
Why did Mazda stop recommending the bon-ami thing?
Hmmm I don't guess we clearanced the seals that well. I used all new seals in the engine. We ground the seals down to make them fit in the rotor, as the manual said. We tried to get them as close to perfect as possible, but I think we went over a bit too far on one or two of them. I also had to use one old seal, because I broke one of the new ones sanding it down. The front rotor was kind of screwed up though, because it was carbon locked in the housing and no matter what we couldn't get it out. So we had to take the front half of the engine apart backwards(front housing first), and then once we got it apart, we had to beat the rotor out of the housing because we couldn't push it out. The engine had been sitting for something like 7 years I figure, though it only had 60k miles on it. I was amazed by the amount of carbon in it. Anyway I think that the seals might be sticking where we hit the rotor because those were kinda tough to get in. We had to sand down the bit where corner seal goes in to get it in, and it still didn't feel as smooth as the other rotor.
I suppose the next thing would be to check for vacuum leaks. I need a gauge or something I guess.
Why did Mazda stop recommending the bon-ami thing?
09-28-2003, 05:16 PM
#24
Senior Member
Join Date: Jul 2002
Posts: 2,315
Originally Posted by ryosuke_fc' date='Sep 28 2003, 11:56 AM
Well my dad went out there and started it this morning, and he said it started by key but didn't want to idle. Strange it starts when cold, but not hot eh?
Hmmm I don't guess we clearanced the seals that well. I used all new seals in the engine. We ground the seals down to make them fit in the rotor, as the manual said. We tried to get them as close to perfect as possible, but I think we went over a bit too far on one or two of them. I also had to use one old seal, because I broke one of the new ones sanding it down. The front rotor was kind of screwed up though, because it was carbon locked in the housing and no matter what we couldn't get it out. So we had to take the front half of the engine apart backwards(front housing first), and then once we got it apart, we had to beat the rotor out of the housing because we couldn't push it out. The engine had been sitting for something like 7 years I figure, though it only had 60k miles on it. I was amazed by the amount of carbon in it. Anyway I think that the seals might be sticking where we hit the rotor because those were kinda tough to get in. We had to sand down the bit where corner seal goes in to get it in, and it still didn't feel as smooth as the other rotor.
I suppose the next thing would be to check for vacuum leaks. I need a gauge or something I guess.
Why did Mazda stop recommending the bon-ami thing?
Hmmm I don't guess we clearanced the seals that well. I used all new seals in the engine. We ground the seals down to make them fit in the rotor, as the manual said. We tried to get them as close to perfect as possible, but I think we went over a bit too far on one or two of them. I also had to use one old seal, because I broke one of the new ones sanding it down. The front rotor was kind of screwed up though, because it was carbon locked in the housing and no matter what we couldn't get it out. So we had to take the front half of the engine apart backwards(front housing first), and then once we got it apart, we had to beat the rotor out of the housing because we couldn't push it out. The engine had been sitting for something like 7 years I figure, though it only had 60k miles on it. I was amazed by the amount of carbon in it. Anyway I think that the seals might be sticking where we hit the rotor because those were kinda tough to get in. We had to sand down the bit where corner seal goes in to get it in, and it still didn't feel as smooth as the other rotor.
I suppose the next thing would be to check for vacuum leaks. I need a gauge or something I guess.
Why did Mazda stop recommending the bon-ami thing?
do this to check vacuum leaks,, very easy. hold engine at about 2k, it will work better
10-12-2003, 02:24 PM
#25
Member
Join Date: Sep 2003
Posts: 50
If you build the motor with used parts you have a chance of it coming in after at least 1000mi. of driving. You said you used all new parts, well 45 psi. with new parts means to me it was not put together right at all. All your symptons are classical low compression.
10-14-2003, 02:10 PM
#26
Senior Member
Join Date: Dec 2002
Location: Queens, New York
Posts: 204
Ya man not to be a bummer, but you need to check your compression again. Do one spark-plug hole at a time. Unplug the connector to the destributor so it wouldn't spark on you and then check each camber for compression. You should get at least 85 psi out of each camber and they should also be closely matched to each other too. In other words 87 for the front rotor 90 for the rear. If not or if either one comes in below 85 psi your going to probably have to go back in their and correct the sealing problems. Just for an example a fresh rebuild with all new seals, clearenced and installed correctly should give you over 100psi compression at each camber. Do this first before you spend anymore time or money and get back to us with some hard figures after.
PK797 NYC
PK797 NYC
10-14-2003, 09:11 PM
#27
Senior Member
Join Date: Dec 2002
Location: Queens, New York
Posts: 204
You really need to do another compression test. Get back to us with some hard numbers. Check one plug at a time and disconnect the plug going to the distributor before you start cranking so you don't get spark. Let us know what you get. P.S. what year/model is it?
PK 797 NYC
PK 797 NYC
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