starting problem, related to overheating?
10-10-04, 12:48 AM
#1
starting problem, related to overheating?
i bought an '87 RX7 TII about 9 months ago, the owner told me it had an overheating problem so i towed it home. i drove the car about 2 weeks before it showed any signs of a problem, i parked the car at a convenience store while i went inside and when i came out 3 mins later the car wouldn't start and acted flooded. i cleaned the plugs and removed the EGI fuse and cleaned it out and got it running and made it the last 4 blocks home with plumes of white smoke behind me and running 3/4+ temp on the guage.
i removed the engine and went through it, the housings appeared ok, flat and the jackets did have some corrosion but repairable. i ported the intake and exahust and completed the overhaul and put the engine in this last week but when i went to fire it up it started and flooded out when i took my foot off the accelerator and then wouldn't restart unless i piched the fuel inlet line then it would only run for a few seconds then die as the fuel bled off. i heard some bubbling in the cooling system and so i removed the cap and it was under pressure and it also smells of fuel vapors... well my first assumption is one of the injectors may be sticking or the regulator is stuck closed and overpressurizing the system, i am going to try putting in some N/A injectors i have lying around with the same resistance to rule out a stuck injector.
this still leaves the fuel vapors in the cooling system though... is there any place else aside from the engine that could cause a problem to cross between the engine and the cooling system? turbo seal or cracks internal maybe?
i have a few more tests to do but i am not liking the way this is looking, what do you all think? are my rotor housings fubared even though they looked ok? have any of you had this problem and it wasn't an internal engine fault? i'm getting annoyed after spending $1k and close to a weeks worth of labor rebuilding the engine only to have it cough at me and i'm praying there is a reasonable explanation.
i have been reading the forums for a while and i know how things work around here, if you plan to say "pull it out again..." give a reason or i will give the stfu reply because it is my time, not yours.
thanks everyone.
i removed the engine and went through it, the housings appeared ok, flat and the jackets did have some corrosion but repairable. i ported the intake and exahust and completed the overhaul and put the engine in this last week but when i went to fire it up it started and flooded out when i took my foot off the accelerator and then wouldn't restart unless i piched the fuel inlet line then it would only run for a few seconds then die as the fuel bled off. i heard some bubbling in the cooling system and so i removed the cap and it was under pressure and it also smells of fuel vapors... well my first assumption is one of the injectors may be sticking or the regulator is stuck closed and overpressurizing the system, i am going to try putting in some N/A injectors i have lying around with the same resistance to rule out a stuck injector.
this still leaves the fuel vapors in the cooling system though... is there any place else aside from the engine that could cause a problem to cross between the engine and the cooling system? turbo seal or cracks internal maybe?
i have a few more tests to do but i am not liking the way this is looking, what do you all think? are my rotor housings fubared even though they looked ok? have any of you had this problem and it wasn't an internal engine fault? i'm getting annoyed after spending $1k and close to a weeks worth of labor rebuilding the engine only to have it cough at me and i'm praying there is a reasonable explanation.
i have been reading the forums for a while and i know how things work around here, if you plan to say "pull it out again..." give a reason or i will give the stfu reply because it is my time, not yours.
thanks everyone.
Last edited by RotaryEvolution; 10-10-04 at 01:05 AM.
10-10-04, 04:44 PM
#3
Lives on the Forum
Ruled out massive vac leaks yet?
Do the plugs have anything other than fuel on them?
Any smoking at startup (when you can get her started, anyway)?
Any bubbles at all in the coolant, or just fuel smell?
How does the oil smell?
Read the injectors out at the ECU while cranking, is there a voltage drop when the key is turned to start? If no voltage to ground even with key on, may be a bad injector circuit.
Does she run rough when she is running?
Do the plugs have anything other than fuel on them?
Any smoking at startup (when you can get her started, anyway)?
Any bubbles at all in the coolant, or just fuel smell?
How does the oil smell?
Read the injectors out at the ECU while cranking, is there a voltage drop when the key is turned to start? If no voltage to ground even with key on, may be a bad injector circuit.
Does she run rough when she is running?
10-10-04, 09:17 PM
#4
i have checked all possible vac leak sources so i would say i have ruled that out, i have had the upper intake off about half a dozen times and every time is the same. i even went through and replaced all the vacuum hoses today as they were all brittle.
only fuel on the plugs, plenty of it and i have 2 sets of plugs i am alternating with and checking them regularly to be sure they aren't fouling.
it smokes but a dark grey color and smells of raw fuel, no coolant. i am an 11 year mechanic and i know what burnt coolant smells like so i am still not so worried about the cooling system as of yet but it appears the injectors are staying open wayy too long or sticking on, i tried an N/A set of injectors and the same problem so it doesn't appear to be the injectors but the signal from the ECM.
the oil smells like oil. :p
i haven't checked the ECM signal to the injectors yet since i was planning on checking the spray pattern when i had it apart but not easy to do with sandwich style injectors/rail so i threw the N/A injectors in for a quick test but it turned out to be a not so quick test when i was through.
when i manually lean out the fuel system and get it started it runs perfect but sounds loaded up, which it is.
side note i found just now, i pulled the ECM out of curiosity because i have heard of cold solder joints in these ECMs and i found about half a dozen cold solders on the input/output pin harness of the board so i will clean them up and resolder them and retry this tomorrow or the next.
let me know what you think so far or if you need any more info.
edit: also to note, i removed the O2 sensor to be sure it wasn't a plugged cat, when the key is on and the fuel pump running i can hear a hissing type of noise from the exhaust O2 sensor hole, which pretty well substantiates that i believe the injectors are sticking/pulsing when they shouldn't be, but from what reason i don't know yet. when cranking the engine with the plugs out there is plenty of fuel coming out but not geysers. things that make you go hmmmm...
another thing to note, when i picked up the car the o2 sensor was not connected at all (broken wire hanging), i replaced it but i wasn't sure of the position on the wiring harness that the O2 sensor connected to so i patched it up to the harness split where the BAC connector sits, also oddly enough the Knock sensor pulled out of its wire and it also uses a solid grey wire on the wiring harness mid harness so it can be easy to mix them up, the wiring diagrams are hard to understand for Mazda, it appears as though they both use a common sense wire to the ECM but that isn't right. if you know whether that is the right spot for the O2 sensor connector i can only assume the knock sensor connects at the split where the intake temp sensor connector is.
only fuel on the plugs, plenty of it and i have 2 sets of plugs i am alternating with and checking them regularly to be sure they aren't fouling.
it smokes but a dark grey color and smells of raw fuel, no coolant. i am an 11 year mechanic and i know what burnt coolant smells like so i am still not so worried about the cooling system as of yet but it appears the injectors are staying open wayy too long or sticking on, i tried an N/A set of injectors and the same problem so it doesn't appear to be the injectors but the signal from the ECM.
the oil smells like oil. :p
i haven't checked the ECM signal to the injectors yet since i was planning on checking the spray pattern when i had it apart but not easy to do with sandwich style injectors/rail so i threw the N/A injectors in for a quick test but it turned out to be a not so quick test when i was through.
when i manually lean out the fuel system and get it started it runs perfect but sounds loaded up, which it is.
side note i found just now, i pulled the ECM out of curiosity because i have heard of cold solder joints in these ECMs and i found about half a dozen cold solders on the input/output pin harness of the board so i will clean them up and resolder them and retry this tomorrow or the next.
let me know what you think so far or if you need any more info.
edit: also to note, i removed the O2 sensor to be sure it wasn't a plugged cat, when the key is on and the fuel pump running i can hear a hissing type of noise from the exhaust O2 sensor hole, which pretty well substantiates that i believe the injectors are sticking/pulsing when they shouldn't be, but from what reason i don't know yet. when cranking the engine with the plugs out there is plenty of fuel coming out but not geysers. things that make you go hmmmm...
another thing to note, when i picked up the car the o2 sensor was not connected at all (broken wire hanging), i replaced it but i wasn't sure of the position on the wiring harness that the O2 sensor connected to so i patched it up to the harness split where the BAC connector sits, also oddly enough the Knock sensor pulled out of its wire and it also uses a solid grey wire on the wiring harness mid harness so it can be easy to mix them up, the wiring diagrams are hard to understand for Mazda, it appears as though they both use a common sense wire to the ECM but that isn't right. if you know whether that is the right spot for the O2 sensor connector i can only assume the knock sensor connects at the split where the intake temp sensor connector is.
Last edited by RotaryEvolution; 10-10-04 at 09:28 PM.
10-10-04, 10:13 PM
#5
Lives on the Forum
See how she runs after the solder joints are fixed, then...
If you know what you're looking at, reading the injector circuit at the ECU will tell you if it's an electrical problem, or an injector mechanical problem...Key on voltage should be exactly the same between the two primary injectors to ground, and idle voltages & above should be the same. If you have one "sticking" electrically you'll see it on the meter- the voltage will be closer to 0v than the other (much closer). See if this link helps...
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/troubleshooting-your-car-ecu-340578/
If you know what you're looking at, reading the injector circuit at the ECU will tell you if it's an electrical problem, or an injector mechanical problem...Key on voltage should be exactly the same between the two primary injectors to ground, and idle voltages & above should be the same. If you have one "sticking" electrically you'll see it on the meter- the voltage will be closer to 0v than the other (much closer). See if this link helps...
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/troubleshooting-your-car-ecu-340578/
10-10-04, 11:51 PM
#6
thanks for the tip, i'll see how the ECU tune up works out first then i may have to test out the backprobing method for further diagnosis.
one last thing i just read up on, i couldn't find any info on the variable resistor anywhere in the Haynes manual so i had no clue what it did until i read through the FSM, i guess it could be the root of all my problems so i will lean that out (there was no seal or blind cap on it and it was set at the full clockwise, rich position) after testing it first and see what happens.
one last thing i just read up on, i couldn't find any info on the variable resistor anywhere in the Haynes manual so i had no clue what it did until i read through the FSM, i guess it could be the root of all my problems so i will lean that out (there was no seal or blind cap on it and it was set at the full clockwise, rich position) after testing it first and see what happens.
10-11-04, 09:40 PM
#7
i resoldered the ECU boards and reinstalled it, i adjusted the variable resistor to the leanest position and retried it, still no luck. i'm looking for the procedures on how to test the resitor and then i will check the relays as they are after the circuit from the ECU in line then i will have to backprobe the ECU and compare the readings.
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10-11-04, 11:09 PM
#8
i tested the variable resistor, though at both ends of the spectrum the resistance was out of range i backed it off somewhat to where they were both in spec and reconnected it, seems a little better as if it is trying harder to start but still won't.
another thing i noticed, the fuel pump runs constantly when the key is on, this is not right is it? i thought it was wired to run when the AFM sees air flow or when the engine is running.
the previous owner was a wiring freak, i see a toggle switch and some other wires under the dash going to who knows where so i will have to trace those out when i have the time. time being the killer of my FC project atm.
i tried finding the injection relays but the FSM and Haynes manual are incorrect as for where they are located and i hate their wiring diagrams... i will find them though by checking the wiring diagram and color matching the wiring to the relay, it's just a PITA though.
soon as i can dig up a tee to hook up a fuel pressure guage i will give a reading for that as well.
another thing i noticed, the fuel pump runs constantly when the key is on, this is not right is it? i thought it was wired to run when the AFM sees air flow or when the engine is running.
the previous owner was a wiring freak, i see a toggle switch and some other wires under the dash going to who knows where so i will have to trace those out when i have the time. time being the killer of my FC project atm.
i tried finding the injection relays but the FSM and Haynes manual are incorrect as for where they are located and i hate their wiring diagrams... i will find them though by checking the wiring diagram and color matching the wiring to the relay, it's just a PITA though.
soon as i can dig up a tee to hook up a fuel pressure guage i will give a reading for that as well.
10-13-04, 12:34 AM
#9
i also forgot to mention it looks as though one of the diodes? on the circuit board of the engine controller got a bit hot, i should replace it but i would hate to install the wrong part onto the circuit board and completely fry the ECM. if someone thinks they can help me out i will post a pic of it.
i checked the fuel pressure, it was a little low but ok at 45 PSI, holds fine. i removed the injector rails and tied up the injectors for a leakage test, no drops in <5 mins. the spray pattern was good but it did look like a huge pulse width (tons of fuel) but i am still new to rotaries so i'm not sure what pulse width is normal for these engines yet. drained all the coolant from the system in case somehow it was getting into the intake through a crack somewhere but still nothing.
stupid car... someone help!
i guess next step is to read all inputs and outputs at the ECM and compare, too bad i can't get engine running readings as well.. :P
i checked the fuel pressure, it was a little low but ok at 45 PSI, holds fine. i removed the injector rails and tied up the injectors for a leakage test, no drops in <5 mins. the spray pattern was good but it did look like a huge pulse width (tons of fuel) but i am still new to rotaries so i'm not sure what pulse width is normal for these engines yet. drained all the coolant from the system in case somehow it was getting into the intake through a crack somewhere but still nothing.
stupid car... someone help!
i guess next step is to read all inputs and outputs at the ECM and compare, too bad i can't get engine running readings as well.. :P
10-13-04, 12:44 AM
#10
Lives on the Forum
Reading those guys at the ECU will tell you if the pulsewidths are that far off or not. Let's say key on is around 12v, then engine running (with the alt pushing the system to about 14v) should yield between 13 and 13.5v (to ground) on the primaries at idle. If it's much lower than that, then the duty cycles just may be out of whack. Never heard of this happening, though, if the various sensors are inputing correct voltages for proper fuel scheduling...
Yep, might as well read 'em all out while you're down there
Yep, might as well read 'em all out while you're down there
10-13-04, 01:06 AM
#11
well the car sat for about 9 months and i started testing sensors, stupid me i tested the pressure sensor as if it was a boost sensor because the haynes manual is quite unclear on the subject and the FSM shows both a boost and a pressure sensor in my car! gotta love publication errors... anyways, i figured that out and that my sensor was working ok so i reinstalled it so the computer wouldn't think it was under boost rather than vacuum.
other problem could be the O2 sensor? i don't know how reliant these systems are on O2 sensor readings but it should be in open loop and not read the O2 at all when the engine is cold right? that would rule out the O2 causing any fuel related issues.
the compression sounds ok and even but i am curious as to what the readings are after the rebuild. the new side seals were a pretty tight fit at .02 mm end to corner seal gap, i also put in some solid corner seals.
anyways, i figured that out and that my sensor was working ok so i reinstalled it so the computer wouldn't think it was under boost rather than vacuum. other problem could be the O2 sensor? i don't know how reliant these systems are on O2 sensor readings but it should be in open loop and not read the O2 at all when the engine is cold right? that would rule out the O2 causing any fuel related issues.
the compression sounds ok and even but i am curious as to what the readings are after the rebuild. the new side seals were a pretty tight fit at .02 mm end to corner seal gap, i also put in some solid corner seals.
10-13-04, 11:15 PM
#12
well close to the worst thing i could think of i found today, i went to start the engine today and it started and ran but i shut it off because of the burn off it was spewing from the exhaust, i tested the compression after it cooled and it was at 20 PSI on both rotors...
question i have is... are the side seals for an '89 different than the ones for an '86-'88? the ones i recieved seemed longer because the clearance was less and i am betting is the problem why i am losing compression, they are probably binding up and sticking. well if i find out they gave me the wrong ones i am going to have a **** fit after spending 2 weeks diagnosing this problem on top of the 2 full days overhauling and installing the engine.
now another question, are the housing seals reusable? if not i may have to kill the parts guys at mazda because i can't afford another $400 gasket set.
question i have is... are the side seals for an '89 different than the ones for an '86-'88? the ones i recieved seemed longer because the clearance was less and i am betting is the problem why i am losing compression, they are probably binding up and sticking. well if i find out they gave me the wrong ones i am going to have a **** fit after spending 2 weeks diagnosing this problem on top of the 2 full days overhauling and installing the engine.
now another question, are the housing seals reusable? if not i may have to kill the parts guys at mazda because i can't afford another $400 gasket set.
10-14-04, 11:42 PM
#14
well i said screw it and put the compression in the back of my mind since it is a fresh rebuild and it isn't broken in yet. i installed a fuel cut off switch so i can manually lean out the fuel system to get it started and i can start it fairly easily now, i ran it until it warmed up then shut it off, it ran decent but the idle was kind of sporatic, idle bounces from 1500-2000 RPMs.
i just hope the housings aren't cracked or something else unvisible, the engine warmed up about normal but began to get warm when i shut it off. i checked the radiator, it was still lukewarm/semi cold whereas the engine was nice and warm and the cooling system was pressurized but the electric cooling fan never came on because the fan switch never got hot enough, seems as though the coolant is not flowing due to a water pump problem or thermostat stuck.
never had this many problems building an american engine...
i still kind of miss my '69 elcamino 400 RWHP 383 stroker that i gave up to keep the TII, i hope she doesn't keep disappointing me like this.
i just hope the housings aren't cracked or something else unvisible, the engine warmed up about normal but began to get warm when i shut it off. i checked the radiator, it was still lukewarm/semi cold whereas the engine was nice and warm and the cooling system was pressurized but the electric cooling fan never came on because the fan switch never got hot enough, seems as though the coolant is not flowing due to a water pump problem or thermostat stuck.
never had this many problems building an american engine...
i still kind of miss my '69 elcamino 400 RWHP 383 stroker that i gave up to keep the TII, i hope she doesn't keep disappointing me like this.
10-15-04, 09:33 PM
#15
crappy overhaul, something i missed so i am pulling it back out tomorrow. the side seals are an issue i will fix but i think i will need a new rotor housing or 2.
anyone want to donate some new ones to me? looks like the 7 is going to sit in my driveway for another 8 months til i can afford to do it all.
anyone want to donate some new ones to me? looks like the 7 is going to sit in my driveway for another 8 months til i can afford to do it all.
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