Hot start issue, searched, tried, and running out of ideas.
03-04-09, 09:08 PM
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Hot start issue, searched, tried, and running out of ideas.
So here's the details...
1987 GXL 13B NA, 155,XXX miles on the original motor. It flooded once and only once on me a few months back, but after pulling the EGI INJ fuse and cranking for 10 seconds 2 times, it fired right up and never did it again to me.
So, I read up on the forums, decided to do the emissions removal and throttle body mod and remove the EGR since I had the block off for it. So, ACV is gone, EGR gone, 5th/6th ports wired open, rats nest gone, vacuum ports and water nipples plugged/capped per rotaryresurrection.com's walk-through, BAC gone, cold start gone, secondary butterflies gone, thermowax gone, new fuel line laid out and vacuum for FPR is coming directly from the intake manifold (nipple sitting directly under secondary fuel rail/injectors) Car fires up beautifully, and feel a lil more oomph on the go. Awesome.
Until the bucking started. Saw it from 3500 and up. Would do it at around 5k as well, so I was certain it wasn't the whole "3800 RPM" scenario. Well, for ***** and giggles, let's change out the fuel filter, since it was rusted on the casing and had "MAZDA" stamped on it. 21 year old filter, what? Change goes well, fires up after priming again. Well, now it only seems to run a tad better, and the bucking problem is gone.
Hiccuped a few times while driving, checked the TPS for *****, no good. Multi-meter reads 1k at idle position, OL at wide open throttle. Swapped for a good used one from a friend's GTU manifold. Adjusted, yahtzee.
Then, the hot start problem started. Pulled EGI fuse, cranked, but still no good. Rolling start with a clutch kick, and she's off. Get home with it, and same friend comes over and suggests, pull the fuel line coming from the filter turn the key and check the pump. Well, it shot maybe an inch or two from the filter outlet. Change the pump. Just my luck too Pep Boys had one in stock at 8:40pm and I got work at 5 am.
5 min's into the job, it starts to drizzle...then rain....then SNOW. I'm not pleased, but I get it done by about 11:30. Drive to the gas station, fill her up full, and she does it again. Except, I didn't have to pull the fuse to get it started. 2nd attempt, it caught after a few seconds.
Injectors? Sure, we'll try. Swapped those out for 4 from a mystery motor. Denso numbers all matched up, pintles all same size, connectors all the same. Matching numbers tell me maching flow rate, matching color too. Swapped all 4 injectors, new o-rings too, and she pulls a hell of alot harder now. Drives better than ever, like a new car.
Till she gets warmed up, and it won't start. Crap. Hot start assist? Changed the IAT sensor with the one from my 88 T2 motor (going carbed so I won't need it there). Still not doing it. Coolant temp sensor maybe? Boy, what a chore that was. Decided to change the thermostat too since I'm there. Both bolts to the thermo fill neck snap inside the water pump housing. ****. Run some numbers, turns out the T2 uses the same sensor, thermostat, and water pump.
So what do I do? I take the T2's water pump housing and throw it on there. Extra nipple next to the lower radiator hose gets a JB weld plug, and all is well. Put everything back together, fill up on some coolant, yadda yadda, fires up, and now the idle is acting a lil off.
Well, juggling the throttle till the motor warms up to re-adjust the idle and top off the coolant, it turns off, and won't come back on. It already has new wires and plugs too, from only about 120 miles ago, the coils are fine too, ohmed them out. Did the poor man's compression when the motor was hot 4 days ago, believe me it was a bitch taking out hot plugs, but I did it one rotor at a time, and got 3 loud solid puffs from each.
The only thing I can really point to, besides the still possible chance of low compression, is the fuel pressure regulator. That's the only thing I haven't touched yet. FPD was changed too, noticed that the original wasn't pulsating on the screw in the slightest bit. My question is, all the bullshit behind me now, can the fuel pressure regulator cause this hot start issue to continue?
Please excuse the novel, but I figured the more information, the less questions, the more answers. I believe the motor may have already had a rebuild of some sort done, as when I did the clutch about 10 months back, I noticed a new rear main oil seal and also you can kind of see gasket sealant/maker in between housings and irons along the outer edges. not a profuse amount, but some that you can notice.
Any help is greatly appreciated!!! And if it's down to a rebuild, well, I got a monster port T2 that i've built going in, but I'd like to finish ordering parts before I pull this NA out.
1987 GXL 13B NA, 155,XXX miles on the original motor. It flooded once and only once on me a few months back, but after pulling the EGI INJ fuse and cranking for 10 seconds 2 times, it fired right up and never did it again to me.
So, I read up on the forums, decided to do the emissions removal and throttle body mod and remove the EGR since I had the block off for it. So, ACV is gone, EGR gone, 5th/6th ports wired open, rats nest gone, vacuum ports and water nipples plugged/capped per rotaryresurrection.com's walk-through, BAC gone, cold start gone, secondary butterflies gone, thermowax gone, new fuel line laid out and vacuum for FPR is coming directly from the intake manifold (nipple sitting directly under secondary fuel rail/injectors) Car fires up beautifully, and feel a lil more oomph on the go. Awesome.
Until the bucking started. Saw it from 3500 and up. Would do it at around 5k as well, so I was certain it wasn't the whole "3800 RPM" scenario. Well, for ***** and giggles, let's change out the fuel filter, since it was rusted on the casing and had "MAZDA" stamped on it. 21 year old filter, what? Change goes well, fires up after priming again. Well, now it only seems to run a tad better, and the bucking problem is gone.
Hiccuped a few times while driving, checked the TPS for *****, no good. Multi-meter reads 1k at idle position, OL at wide open throttle. Swapped for a good used one from a friend's GTU manifold. Adjusted, yahtzee.
Then, the hot start problem started. Pulled EGI fuse, cranked, but still no good. Rolling start with a clutch kick, and she's off. Get home with it, and same friend comes over and suggests, pull the fuel line coming from the filter turn the key and check the pump. Well, it shot maybe an inch or two from the filter outlet. Change the pump. Just my luck too Pep Boys had one in stock at 8:40pm and I got work at 5 am.
5 min's into the job, it starts to drizzle...then rain....then SNOW. I'm not pleased, but I get it done by about 11:30. Drive to the gas station, fill her up full, and she does it again. Except, I didn't have to pull the fuse to get it started. 2nd attempt, it caught after a few seconds.
Injectors? Sure, we'll try. Swapped those out for 4 from a mystery motor. Denso numbers all matched up, pintles all same size, connectors all the same. Matching numbers tell me maching flow rate, matching color too. Swapped all 4 injectors, new o-rings too, and she pulls a hell of alot harder now. Drives better than ever, like a new car.
Till she gets warmed up, and it won't start. Crap. Hot start assist? Changed the IAT sensor with the one from my 88 T2 motor (going carbed so I won't need it there). Still not doing it. Coolant temp sensor maybe? Boy, what a chore that was. Decided to change the thermostat too since I'm there. Both bolts to the thermo fill neck snap inside the water pump housing. ****. Run some numbers, turns out the T2 uses the same sensor, thermostat, and water pump.
So what do I do? I take the T2's water pump housing and throw it on there. Extra nipple next to the lower radiator hose gets a JB weld plug, and all is well. Put everything back together, fill up on some coolant, yadda yadda, fires up, and now the idle is acting a lil off.
Well, juggling the throttle till the motor warms up to re-adjust the idle and top off the coolant, it turns off, and won't come back on. It already has new wires and plugs too, from only about 120 miles ago, the coils are fine too, ohmed them out. Did the poor man's compression when the motor was hot 4 days ago, believe me it was a bitch taking out hot plugs, but I did it one rotor at a time, and got 3 loud solid puffs from each.
The only thing I can really point to, besides the still possible chance of low compression, is the fuel pressure regulator. That's the only thing I haven't touched yet. FPD was changed too, noticed that the original wasn't pulsating on the screw in the slightest bit. My question is, all the bullshit behind me now, can the fuel pressure regulator cause this hot start issue to continue?
Please excuse the novel, but I figured the more information, the less questions, the more answers. I believe the motor may have already had a rebuild of some sort done, as when I did the clutch about 10 months back, I noticed a new rear main oil seal and also you can kind of see gasket sealant/maker in between housings and irons along the outer edges. not a profuse amount, but some that you can notice.
Any help is greatly appreciated!!! And if it's down to a rebuild, well, I got a monster port T2 that i've built going in, but I'd like to finish ordering parts before I pull this NA out.
03-04-09, 09:47 PM
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the "rats nest" holds a solenoid (black plug/sticker one i believe) that is used for hot start assist. It is plumbed to the FPR. If the coolant is over 76* the solenoid is turned on which bleeds all vacuum from the FPR (Highest fuel pressure) for 90 seconds, at which point the solenoid is turned off and manifold vacuum is allowed to control the FPR.
You seem to know what you are doing. so my only other idea is the BAC valve.
You can try this the next time you go to hot start:
Remove the vacuum line for FPR
Plug the manifold
Turn the key.
If it starts up easy then you probably need to put the Hot-Start solenoid back in.
-Pat
You seem to know what you are doing. so my only other idea is the BAC valve.
You can try this the next time you go to hot start:
Remove the vacuum line for FPR
Plug the manifold
Turn the key.
If it starts up easy then you probably need to put the Hot-Start solenoid back in.
-Pat
03-04-09, 10:12 PM
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Here's the thing, though. Of all the posts I've seen of people removing the solenoid/vacuum rack, no one has reported that they had to revert back to their FPR solenoid for hot start issues, which is reason why i thought the FPR itself may be faulting out.
However, I will give your method a try and see what the results are. Thanks for that bit of info!
However, I will give your method a try and see what the results are. Thanks for that bit of info!
03-07-09, 05:52 PM
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Installed FPR solenoid (orange connector, used solenoid from 88 T2 rack since it's going carb) and placed vacuum line back on nipple behind throttle body (bottom most according to vacuum diagrams) and still no luck. Upon further searching, I cant recall the site, but according to the CEL code flashed pertaining to the ECU, it says a faulted O2 sensor will throw the ECU into a noncorrective/open loop? mode. Well, leads me to believe that might be the issue although I changed it last year. A few fireballs here and there I'm sure it singed the sensor so I'll try changing that tomorrow.....this really sucks lol
03-08-09, 10:29 AM
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Ya'll really and truly need to drop the idea of the FPR solenoid causing the flooding problem.
In case you missed it, when your cranking an engine over during the start phase........there ain't no darn vacuum there to effect the FPR. The FPR duing start is going to supply approx 39psi to the fuel rails........because thar isn't any damn vaccuum pulling on the FPR's diaphram.
The BAC does aid in hot and cold starts. When you hold the key to START, the BAC goes and stays full open, allowing in a bit more air. I'm not saying that the lack of a BAC is your problem, but having a BAC helps. Once the key is let go, the BAC returns to its normal duty cycle.
Your best bet is to make a fuel cut switch or depin pin 3B the next time the engine is hot. Lack of 3B (start signal TO the ECU) means the ECU uses the afm for starting fuel instead of the start fuel map internal to the ECU.
Oh, and don't even give the slightest thought of the 02 sensor being the problem. It's only in the loop during steady driving over approx 1700rpms or so. Not a player.
Tee in a fuel pressure gauge to the pressure line coming out of the fuel filter. Key to ON, engine off. The pressure will read approx 37-39psi on a stock car with STOCK fuel pump. A Waldo fuel pump will probably cause the pressure to be quite a bit higher than 37-39psi. Don't KNOW that, but suspect that.
In case you missed it, when your cranking an engine over during the start phase........there ain't no darn vacuum there to effect the FPR. The FPR duing start is going to supply approx 39psi to the fuel rails........because thar isn't any damn vaccuum pulling on the FPR's diaphram.
The BAC does aid in hot and cold starts. When you hold the key to START, the BAC goes and stays full open, allowing in a bit more air. I'm not saying that the lack of a BAC is your problem, but having a BAC helps. Once the key is let go, the BAC returns to its normal duty cycle.
Your best bet is to make a fuel cut switch or depin pin 3B the next time the engine is hot. Lack of 3B (start signal TO the ECU) means the ECU uses the afm for starting fuel instead of the start fuel map internal to the ECU.
Oh, and don't even give the slightest thought of the 02 sensor being the problem. It's only in the loop during steady driving over approx 1700rpms or so. Not a player.
Tee in a fuel pressure gauge to the pressure line coming out of the fuel filter. Key to ON, engine off. The pressure will read approx 37-39psi on a stock car with STOCK fuel pump. A Waldo fuel pump will probably cause the pressure to be quite a bit higher than 37-39psi. Don't KNOW that, but suspect that.
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03-08-09, 05:03 PM
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Tee in a fuel pressure gauge to the pressure line coming out of the fuel filter. Key to ON, engine off. The pressure will read approx 37-39psi on a stock car with STOCK fuel pump. A Waldo fuel pump will probably cause the pressure to be quite a bit higher than 37-39psi. Don't KNOW that, but suspect that.
03-08-09, 05:16 PM
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You'd have to repin it on cold days. Or make a switch to that wire that makes/unmakes it so you can determine if it needs to be made or not. In Main you'd need it pinned up for the cold days.
If it's depinned it cuts the duty cycle down to something like 6ms vs with it pinned up at 18ms. I made those figures up because I don't remember the exact figures.
Or just make a fuel cut switch. Search for how to. But sometime, once you know how to depin that wire from the plug, get the engine HOT and then depin that wire and go drive around stopping and starting the car numerous times and determine for YOURSELF if that is or is not a great help on HOT starts. Cold starts in Maine would be tricky with it depinned.
Put a fuel pressure gauge on that fuel pump and see what it's output is. As in deaheaded. As in the pump and the gauge being the only items connected when you check the pressure. Stock fuel pressure is given in the FSM, Fuel and Emissions Section. Like 64-80 psi pump pressure. But if gthe gauge is tee'd into the presssure line with everything connected up, the pressure should be 37-39 key ON, engine OFF, and approx 28-32psi at idle with the vacuum hose on the FPR.
If it's depinned it cuts the duty cycle down to something like 6ms vs with it pinned up at 18ms. I made those figures up because I don't remember the exact figures.
Or just make a fuel cut switch. Search for how to. But sometime, once you know how to depin that wire from the plug, get the engine HOT and then depin that wire and go drive around stopping and starting the car numerous times and determine for YOURSELF if that is or is not a great help on HOT starts. Cold starts in Maine would be tricky with it depinned.
Put a fuel pressure gauge on that fuel pump and see what it's output is. As in deaheaded. As in the pump and the gauge being the only items connected when you check the pressure. Stock fuel pressure is given in the FSM, Fuel and Emissions Section. Like 64-80 psi pump pressure. But if gthe gauge is tee'd into the presssure line with everything connected up, the pressure should be 37-39 key ON, engine OFF, and approx 28-32psi at idle with the vacuum hose on the FPR.
03-08-09, 05:24 PM
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ME is Maine, MA is Massachusetts a few people get that confused too lol, so I'm not too cold here thankfully. Found the fuel cut switch write up here in the FAQ's for 2nd Gen. Will throw that one in for the time being, temporary, since I'm just going to start my swap in a week or 2. Hate not being able to drive her around..... Hailers, Pat, thanks for the help, greatly appreciated!
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