Weird problem, car cranks, starts, and immediately dies (not fuel?)
 

ok...

so, my car technically 'starts'

I crank the car, the starter disengages, and the car gets to about 700-900 rpm and then just falls on its face.. its weird.

I dont think its fuel, because I have an aftermarket rail and FPR with a gauge attached. The gauge shows as high as 50psi when cranking and *almost* starting, but it still dies.

Originally, I thought for sure it was a fuel problem. But after having a friend crank the car while I watched the gauge, now Im prety sure thats not it.

I dont know what it could be, any ideas? One thing I noticed is it seems that my PFC is reading a screwed up vacuum/boost. First it read at -27 while cranking (about what it should be when the car is off) and now it reads +0.37 mmHg. it is def. not making .37mmhg (like 5-6psi) just cranking!

Only thing I can think of is this weather is messing wiht my car somehow, its very cold here and my car sits outside

My car is non-seq, I have an aftermarket secondary rail (rx-7store) and 1600 secondaries, stock 550s...

I am pretty baffled, dont know what this could be... :(

-scott

its the map sensor its unpluged

Stock Boost Sensor (MAP)?

Make sure you are still on the "normal" setting under the PIM settings.

*edit* Also go to the sensor check screen and watch the voltage on the MAP sensor (I think it labeled as PIM under that screen), it should be around 1.5volts when at atmosphere/cranking.

yea stock boost sensor....

the denso boost sensor connects to the throttle body right by the stock elbow, right??

This rubber hose was actually disconnected.... hrmm.. but it didnt fix the problem :(

I am going to go back out and look at some things...

I will look through the PFC menu and check what rotorjoe said...

-scott

sensor check had PIM volt at 2.64 v

Now im even more confused since the MAP sensor was off, but plugging it back in did nothing, unless I put it in the wrong place..

ahh, hold on. It was a guess off the top of my head what the voltage should be while the car is off. I don't have my car with me today so I'll have to seach a bit.

appears the map sensor is ok

really weird how the map sensor WAS unplugged, and i plugged it in, and it didnt fix the problem!

the map sensor connects right after the elbow before the UIM, right? (the TB)

Yes.

that thread didnt really help me.. map sensor is plugged in, car still does the same thing..

Yeah, After reading it again in more detail I edited my post. You're right it didn't help.

But I think you may be right in thinking the map sensor is ok and we may have gotten side tracked. But can you keep the car running? With the vacuum hose off it could have flooded the car a bit and just needs to be warmed up?

I think I may be out of ideas and will let someone else jump in. Sorry.

im about at the point where i need a battery jump, battery is pretty much dead from cranking..

car does not stay running, if im lucky itll hit about 800-900 rpm before it cuts out, seems to build pefect compression through...

im thinking this may be due to weather, its 15 F here right now...

That's not that cold.:p:

I found this also which will give you the voltages at specific pressure levels. Double check yours but I think its fine now.
https://www.rx7club.com/showthread.p...ressure+sensor

I guess another question would be, did you change anything inbetween the time it was running and now?

hey rotorjoe,

I got the car running...

I guess it was the map sensor. I guess it took a minute for the car to get back to normal once it was plugged back in.. Anyways, car runs well

Thanks a lot joe, I really do appreciate all your help


Scott Meyer

I was just about to say "I'm out for the day, good luck."

Well, I'm glad I could help. You're welcome. After a bit I didn't think I was helping.

:bigthumb:
Joe

now if that isnt team work.....i dont know what is.....gotta love this place..!!
:bigthumb:

its because without that pluged in it gives it to much gas and fowels out the spark plugs.
then it will take a minute to get back to norm. or like mine you may have to replace the sparkplugs.
or just warm up then go tear up the road blow it out.

I'm kinda having the same issues. When cranking, I'll get around 550-800 rpms, here it kicking but die immediately after i let go of the starter. I just changed plugs and fresh battery and still having the same issue.

I am having the same problem at the moment.

However, I know the car is missing gas through logs. Before car runs <1s, add 30% duty car runs 1.5s add 50% duty car runs 3s.

New plugs, all new injectors, fuel hoses in the correct order, map sensor is Ok it is giving out proper output, TPS is working as it should be. Only thing I can think of is the pump does't maintain voltage as it needs to be so this would have to be a problem in the fuel pump wiring.

Solved.

After having performed the Stock Pump rewire and still having the same problem I started thinking. To come to the realization that the only functionally different part I had installed is the Coil Relocation Bracket with some homemade MSD spark plug wires. I had read elsewhere that some people has to gap the spark plugs because of these wires so it got me to thinking about timing.

The result, I added degrees to the IGL in idle and boom everything works, rough but works guess it is time to start tuning out the bugs now.

Back to nada I am stumped.

Turned out to be a problem with the FJO box, apparently mine is not happy running high impedance and low impedance injectors together.