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93 RX7 wonít start

Old 03-10-19, 05:12 PM
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93 RX7 wonít start

So, I have an R1 FD rx7 RHD. Iím going to start by listing engine mods so you guys can get an accurate description of my car before diagnosing.
- Engine rebuilt 1000ish km ago
- stock twin turbos
- streetport
- simplified vacuum lines
- hks intakes
- side mount coil packs(brand new)
- OEM fuel system(brand new primaries)
- Apexíi PFC ECU(running base map)
- No catalytic converter, hks downpipe, mazdaspeed muffler

So starting at the beginning, after the rebuild the car didnít start right away because one of my CAS was bad. After replacing it the car started up right away, a couple days and breaking the new rebuild in by letting it idle and the car randomly dies while idling. After trying and trying to get it started it will not start it stutters Iím cranking like something is preventing it from starting. After multiple diagnosis we cannot figure it out. I try replacing one of my primary injector connectors and cleaning the ECU grounds under the UIM. Car starts up and seems fine, although has trouble starting will start. I drive it all summer without any real issues, It doesnít like to hot start though(yes I checked compression it is good). I put it away for winter and start it up this spring everything seems good. Driving for maybe 2 weeks and then one Sunday it dies while idling, try to start it back up and the same ďStutteringĒ while cranking is happening. I tried deflooding many times, and replaced the primary injectors. Cleaned the plugs every deflood. It is getting fuel, and it is getting spark. I re did the vacuum lines about a week ago so I know no vacuum leaks are present. One time it started roughly and it idled beautiful and then at about 57 degrees Celsius it died again before we could get to the throttle. I have added grounds, replaced sensors, checked spark, fuel, jumped the car, Iíve tried everything I can think of but something is stopping it from starting. Iím inclined to think it is something electrical but donít even know where to start. Please any suggestions or opinions are welcome, I have 10 months to get the car up and running well so I can ship it back home to the states from Germany where Iím stationed currently
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Old 03-15-19, 04:27 PM
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Welcome to the board.

Well, I tend to agree with your assessment - that it's probably an electrical thing. In particular, you mentioned having to change one of the crank sensors before. Maybe you need to start fishing around the engine harness in that area. I'm not an FD guy, so get your grain of salt, but you have nothing to lose by looking into it.
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Old 03-15-19, 06:15 PM
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Sounds a lot like a fuel issue to me. Check your fuel pressure. Actually check your fuel pressure. See that it HOLDS 43psi when you prime the pump. Also check that the pump itself is good and replace the oring at the stand pipe for the fuel pump.
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Old 03-16-19, 05:35 AM
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Originally Posted by cr-rex View Post
Sounds a lot like a fuel issue to me. Check your fuel pressure. Actually check your fuel pressure. See that it HOLDS 43psi when you prime the pump. Also check that the pump itself is good and replace the oring at the stand pipe for the fuel pump.
Can I put in an aftermarket FPR with my OEM fuel system and have no problems?
Also would not enough fuel pressure cause the car not to start? Or have a hard time starting?
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Old 03-16-19, 10:42 AM
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Low fuel pressure will cause exactly that, yes. The problem becomes worse when the car is warmed up, if it starts at all.

You can put an aftermarket fpr with stock rails so long as you remove the stock one and attach the necessary fittings to the rail...... although there's no point to that. There are inline fuel pressure gauges that are used for diagnostics. If you don't have access to one then you can just replace the oring at the stand pipe and see if that helps and we can go from there.

it's just troubleshooting without the proper tools to confirm suspicions is extremely difficult since you would just be blindly replacing parts until the issue went away.

another way to check fuel pressure is watching injector duty cycle. An abnormally high duty cycle compared to the load is giveaway and also hitting 100% with relative ease is an indication. If you have a commander with your pfc then you can check it through there.
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Old 03-16-19, 11:18 AM
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Originally Posted by cr-rex View Post
Low fuel pressure will cause exactly that, yes. The problem becomes worse when the car is warmed up, if it starts at all.

You can put an aftermarket fpr with stock rails so long as you remove the stock one and attach the necessary fittings to the rail...... although there's no point to that. There are inline fuel pressure gauges that are used for diagnostics. If you don't have access to one then you can just replace the oring at the stand pipe and see if that helps and we can go from there.

it's just troubleshooting without the proper tools to confirm suspicions is extremely difficult since you would just be blindly replacing parts until the issue went away.

another way to check fuel pressure is watching injector duty cycle. An abnormally high duty cycle compared to the load is giveaway and also hitting 100% with relative ease is an indication. If you have a commander with your pfc then you can check it through there.
What O ring are you talking about? Iím not sure weíre the stand pipe is?
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Old 03-16-19, 10:00 PM
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When you pull the fuel pump hanger from the gas tank, at the top of the of the fuel pump there will be a hat shape object. Under it will be the top of the fuel pump, an o-ring and some other peice that is split in half. Replace the o-ring. The pipe that goes from the top of the fuel pump to the hanger is the stand pipe......... or so as I'm referring to it anyway.

you can get the o-ring from mazda or you can get the Dorman fuel injector o-ring variety pack from auto zone or something..... I've used both options.
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Old 03-17-19, 07:03 AM
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Originally Posted by cr-rex View Post
When you pull the fuel pump hanger from the gas tank, at the top of the of the fuel pump there will be a hat shape object. Under it will be the top of the fuel pump, an o-ring and some other peice that is split in half. Replace the o-ring. The pipe that goes from the top of the fuel pump to the hanger is the stand pipe......... or so as I'm referring to it anyway.

you can get the o-ring from mazda or you can get the Dorman fuel injector o-ring variety pack from auto zone or something..... I've used both options.
gotcha! I will pull mine out and replace it and then get back to you with some pics
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Old 03-17-19, 01:28 PM
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NY

Sounds to be a fuel related issue. Iíd start with running a FPR to see where you are sitting. You can also check your plugs and see if they are dry or wet. This will kind of tell you if you have to much fuel being dumped or not enough.
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Old 03-18-19, 04:29 AM
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Originally Posted by Zero_Cylinders View Post
Sounds to be a fuel related issue. Iíd start with running a FPR to see where you are sitting. You can also check your plugs and see if they are dry or wet. This will kind of tell you if you have to much fuel being dumped or not enough.
ive been checking the plugs they have fuel on them and it doesnít seem to be too much, but I wasnít sure so I was deflooding the car like 10 times and trying to start it but every time it did the same thing
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Old 03-18-19, 11:01 AM
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Originally Posted by cr-rex View Post
When you pull the fuel pump hanger from the gas tank, at the top of the of the fuel pump there will be a hat shape object. Under it will be the top of the fuel pump, an o-ring and some other peice that is split in half. Replace the o-ring. The pipe that goes from the top of the fuel pump to the hanger is the stand pipe......... or so as I'm referring to it anyway.

you can get the o-ring from mazda or you can get the Dorman fuel injector o-ring variety pack from auto zone or something..... I've used both options.
my pump and hanger assembly looks brand new. But I have a theory. I have a hose going from my primary rail to secondary that is not the OEM one and it very slightly leaks when I turn the ignition on so Iím going to replace it and see if that is the problem.

Last edited by Ludy Bahneman; 03-18-19 at 11:05 AM.
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Old 03-18-19, 11:53 AM
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Originally Posted by cr-rex View Post
When you pull the fuel pump hanger from the gas tank, at the top of the of the fuel pump there will be a hat shape object. Under it will be the top of the fuel pump, an o-ring and some other peice that is split in half. Replace the o-ring. The pipe that goes from the top of the fuel pump to the hanger is the stand pipe......... or so as I'm referring to it anyway.

you can get the o-ring from mazda or you can get the Dorman fuel injector o-ring variety pack from auto zone or something..... I've used both options.

Also, I am not running an OMP, Air Pump, AC, or Power steering. I was running the OMP before the rebuild, before all this difficulty starting issue.
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Old 03-19-19, 02:54 PM
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Originally Posted by Zero_Cylinders View Post
Sounds to be a fuel related issue. Iíd start with running a FPR to see where you are sitting. You can also check your plugs and see if they are dry or wet. This will kind of tell you if you have to much fuel being dumped or not enough.
Put in the new OEM FPR and some new spark plugs. Rx7 started, idled fine for awhile but I noticed at idle it was at +0.01 kpa and then occasionally would drop to vacuum and the idle would get shaky or it would rev way high. And then one time it dropped to like -145.0 kpa (vacuum Iím assuming) and the idle was at like 1600 forever and it pulse idled for a while before I tried adjusting the idle screw and it eventually died cause I think it was too low. Also my Pulsation dampener on the primary rail is leaking bubbles a tiny bit while the ignition is turned to on position. When I revved it it sounded super choppy and not smooth at all.

Last edited by Ludy Bahneman; 03-19-19 at 02:59 PM.
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Old 03-19-19, 03:01 PM
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youve got a lot more going on than it seems. any fuel leak is unacceptable regardless of how minor. if those are your idle numbers then theres 2 possibilities: theyre accurate and you and have a serious problem that i cant explain or you have a bad map sensor. replacing the oem fpr wont yeild any results. its a very simple part and it failing is infinitely unlikely. you already did so, its too late now. all the things you have deleted dont matter since you have a power fc but since you deleted the omp, you better be pre-mixing.

delete the pulsation damper, fix your leaks, replace the map sensor and try again.
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Old 03-19-19, 03:15 PM
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Originally Posted by cr-rex View Post
youve got a lot more going on than it seems. any fuel leak is unacceptable regardless of how minor. if those are your idle numbers then theres 2 possibilities: theyre accurate and you and have a serious problem that i cant explain or you have a bad map sensor. replacing the oem fpr wont yeild any results. its a very simple part and it failing is infinitely unlikely. you already did so, its too late now. all the things you have deleted dont matter since you have a power fc but since you deleted the omp, you better be pre-mixing.

delete the pulsation damper, fix your leaks, replace the map sensor and try again.
Iíve already replaced the MAP sensor, just waiting on a hose to fix the fuel leak. And do you know what I would need to delete the pulsation dampener? My injector duty also seems high at idle my idle was about 1100 and the injector duty was at 15%. Yes I am premixing

Last edited by Ludy Bahneman; 03-19-19 at 03:18 PM.
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Old 03-19-19, 05:22 PM
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There's a write up for deleting it that goes into detail. I mentioned earlier that higher than normal injector duty is a sign of low fuel pressure. Have you checked your fuel pressure yet?
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