Guys I have a motor I swapped from my s5 vert into my s5 coupe. Everything ran great before the swap.

I found a few various things I thought that could have caused this issue. When I first did the swap it was sort of hard to start but got worse after I thought I flooded it bad a few times.

I have replaced the spark plugs, fuel pump, filter.

It will crank forever before finally catching and running. Once it is warm, runs like a champ. If I shut it off it still acts the same, but not as bad depending on how long it has sat.

I will say this. It is not flooding. I will pull the plugs out and they are dry as a bone. It seems more like a spark or fuel issue related to something not being plugged in right.

Usually it takes about 30 seconds to a minute of constant cranking to start. Attempted deflood makes it worse.

I let it sit for a few weeks while I had the 20b f and when I went to crank it it drained the battery, but once it starts, acts like nothing was wrong. No smoke or anything.

I went to make a vid and ironically it took a lot less time than usual which kinda pissed me off. Anyhow, just watch the vid and image this times five. Listen really closely and you can see how it is different than a flooded motor.

Listen to the spot RIGHT before it finally starts and imagine it doing that for about 20 seconds. It is almost running on its own but not quite. Ill turn the key off and it will shut down. A few more times and it runs. It has to be something will fuel or spark and I cant figure which. You would think with proper fuel though it would flood by itself just from the repeated attempts and shut downs, or I would see some smoke.

I dont know, check it out and give me some thoughts, laugh at my stupid *** in the vid.

http://www.youtube.com/watch?v=MZOMIXlCvrc

 

that idle is high, i am guessing the car wasn't warmed up? I saw your other posts and someone mentioned checking for vacuum leaks. This would cause a hard start.

This sounds exactly like my engine when it gets flooded and I have to play with the gas pedal to get it started. So taking my example, I would say you have some sort of a vacuum leak that is allowing too much air to get into the combustion process, this could be due to vacuum hoses or maybe even the throttle plate is too open? But you did say your not flooding so I am not going to mention it although this is what my car does when it is flooded. These are some suggestion I can offer you. I have an s5 vert by the way.

Check those things out and let us know what is going on. Also do you have any pending DTC codes that would indicate a misconnected sensor.

 

i dont have way of checking codes, and I had one hose that was not connected it and I have since connected it and it is still doing the same thing. I have looked all over and not seeing any leak.

 

Any time I hear that sound of cranking but struggling to start, it brings back memories of lost compression on my old car. Those of us who have been there will tell you to check the compression asap. Although obviously in the vid it wasn't that bad.

then again its odd that its not flooding. Does it run well when it does finally start up?

 

you might check compression, but it may also be worth testing the water thermo sensor on the back of the thermostat housing.

 

+2 on the compression test.

You didn't by chance accidentally drop the motor when swapping it did you? It's VERY common for rotarys to have a hard time starting when the rotor bearings and stat gears are starting to go out.

 

runs great when it starts. The first second after it starts it was like it never happenned. When it is flooded it still acts mad at you for a few minutes. I also noticed the exhaust sounded awful muffled like it was further away. That only happenned once.

I have a hard time believing that the engine ran and started perfectly before I did the swap. Moving the engine from one car to the next does not lower compression. I do need to check it just in case. I have had a motor with low compression and had a hard time starting because it seemed to flood alot. This is oddly different.

I also have had the thermo sensor on the back not plugged in for about a month in the winter and remember quite well what that was like until I fixed it. So I know it isnt that.

What would happen if my fuel filter was on backwards??

 

Also when the car is flooded it whines. This thing lopes well and it gets to the point where it is almost running on its own but like it isnt getting enough fuel. If you also do it long enough you will hear small backfires. It is not flooded for sure.

Also the vid is the ONE time it started semi fine. Usually after a day of sitting it takes about 30-60 seconds of constant cranking.

 

Dirty/stuck injector is very possible. Does the exhaust smell like its dumping fuel or not getting enough while cranking?

 

you know when I first put the motor in I had the fuel lines backwards for a while. You think this might have done something? And during cranking I dont smell much fuel at all.

 

ok i did a compression check but not sure I did it right.

I used the autozone check with the bleeder valve on it so I could not read pulsles and the thing seemed to leak a little. I wiggled it around and the gauge stayed a constant 70lbs on both rotors. I wonder why it was the same exact reading on both rotors. And wouldnt I have at least one face with better compression?

I also didnt feel like i was able to adapter to bottom out in the spark plug hole. That might have made an impact, but if that was the case the checker would be leaking and it stayed where it sat.

I wonder........

 

wait......am I supposed to hold it at open throttle when doing a compression check? Would this make a difference?

 

yes, there will be a pressure drop across the throttle plate. you want to have it down to minimize this. and best to have a battery charger or booster pack hooked up as well so your cranking at the same speed all the time.

 

compression check was 85lbs on both rotors with a different checker, plugged to the battery and at WOT.

 

how does your car idle? at what speed and is the idle a bit bouncy?

Check this thread out:

https://www.rx7club.com/showthread.p...=hard+starting

You said you installed the fuel lines backwards, could it be possible the fuel pressure regulator got damaged while doing this due to the pressure going in backwards?

If you have any extra ones on hand, I would check this out.

 

you could try pinching off your return line and see if it starts right up, that would point to the fuel pressure reg.

 

Hmm. I am defintitely going in a new direction here. I will go ahead and try that and see what happens. I have a spare s5 sitting around. What do you guys think about those compression numbers.

 

compression is sorta low but should be ok

 

my car was having the exact same problem. i changed my wate thermo sensor and it hasnt happened since. i would try doing that if i were you. i got mine off mazdatrix for i thinl like thirty bucks of so.

 

No. I have had that issue before. It is quite a bit different. Hard as hell to start and runs rough until it warms up. This thing doesnt want to start, but as soon as it does, it runs like a champ.

I am willing to bet I fucked up the FPR having stuff hooked up backwards.

 

I second the water thermo sensor. That gave me similar problems in the past. Sometimes it would be hard to start and other times it would have issues when it was finally warmed up. Might be worth checking out just to mark it off the list.

 

Dude,

I am telling you guys I had that problem last year. I know EXACTLY what my car does without it plugged in. It is similar but different. This car runs great the second I get it to crank, with the thermosensor this was not the case. I have already checked it twice and it was fine.

 

ok I have clamped off the return line and same ****.

 

First things to consider:

1. Have you removed any emissions/idle control systems such as the BAC valve or the thermowax?

2. If you push the gas pedal down 25-50% during cranking, does it crank over better?

Now we just go down the line, considering fuel, spark, and air.

Let's assume that compression is fine, and honestly I think it probably is because bad compression leads to hot start problems more than anything else especially if you have worn side seals. During cranking, the primary injectors fire together in batch mode. The fuel injection amount is determined by the "Start" signal which then accesses the water temperature vs injector pulsewidth cranking map. So if the sensor is plugged in and it's relatively accurate (they DO read inaccurately, either too cold or too hot, I have seen it), you can bet the injectors are opening enough as long as the primary's are ok.

Since the car still starts and runs ok under most conditions, the fuel pressure issue is not likely. During cranking, the engine is not under vacuum really, and one of the main purposes of the FPR is to lower fuel pressure when the engine is under vaccum. The FPR doesn't do a whole lot during cranking. According to the training manual, cranking ignition timing is fixed at 5 degrees leading advance, 5 degrees trailing advance (so a split of 0). So if your crank angle sensor is installed correctly (or is at least close), ignition timing should not be an issue. Since the car seems to run fine most of the time, I highly doubt it is a spark issue unless you are getting other signs of spark problems or timing problems.

I am beginning to suspect that you are not getting enough air for a quick, smooth start. The amount of air that enters the engine during cranking is determined by:

1) throttle opening angle. On a cold start, this is highly dependent on your fast idle cam/thermowax system. The fast idle cam opens the primary butterfly more, and then hot coolant eventually pushes down the thermowax (rotating the fast idle camdown). The result is an idle of 750 mostly through a combination of the primary throttle valve opening angle and the help of the BAC valve. Eliminating the thermowax certainly does not help cold start.

2) accelerated warmup system: this solenoid valve is what shoots you up to 3000 rpm on a stock car. A lot of people eliminate it, and Jspec cars don't even have it, but it definitely helps the car start. I'd certainly keep it off though and not worry about it.

3) BAC valve. During cranking this goes to nearly full open. If it has been removed or it is clogged, that will hurt cold starts as well, in addition to dropping the idle when electrical load or power steering is applied. Checking its resistance and cleaning this would help if you still have it, as would putting it back in if you have removed it. People often forget that 100% complete "emissions removal" can result in "driveability removal."

So does giving it more air during cranking help at all? You give it more air by putting the pedal down some (opening the TB butterflies), as long as the pedal doesn't go down so much that it goes into flood clear mode. Note that there is a diagnostic list/procedure in the non turbo fuel and emissions control section of the s5 FSM. See pages F1-40 and F1-13 . The lower the number in the "boxes" of the diagnostic chart, the more important it is to check that particular item.

 

You are the man! I appreciate the time and attention.

Here is another vid of it.

BTW my girl was in a car next to mine revving the engine for the jump

http://www.youtube.com/watch?v=YE5jCU3-k5Y