So I have about 300 miles on a new streetported rebuild that the famous Howard Coleman has done for me. Car is highly modified, single turbo, upgraded fuel system, removed OMP, etc. The motor is running smooth and driving like a champ. I haven't taken the car into boost or over 3.5k as I am still breaking the motor in, but the other day I had some trouble starting the car.

I drove the car probably 20 or so miles and then stopped off at a local grocery store. Came back out about 10 minutes later and when to start the car and the car was turning over but it wouldn't catch. I had to keep turning the car over for about 10 seconds and blip the gas when it sounded like it was about to start and it finally started after a few tries.

I know when I first bought the car it had hot start problems which meant low compression...did a compression test and it was time to rebuild. If I'm having this trouble now, do you think it's time for a compression test or could it just be heat soak?

 

check your fuel pressure with key on engine off, see if it holds. If not, you might have a leaky injector which is very common causing a hard to start issue after it sat.


p.s.
for a newly rebuild, I wouldnt say you have bad compression. But it could be a possibility. But before I do anything else, get that fuel pressure test and make sure you arent having a issue with the fuel system. IF the fuel system holds pressure, then i'll give it a try to check the compression.

-AzEKnightz

 

I've had no problems with my fuel pressure since the rebuild. When just on accessories, it would hold 38psi but I will double check when I get home today. I'm thinking it may be time for new spark plugs too possibly. I already have brand new plugs just wanted to put them in after break in.

 

i had hard hot starting problems after my first rebuild, compression was low. got a 2nd rebuild and compression was much better and hot starting was much better. they also say compression will build after a bunch of miles breaking it in. I did not see much increase in compression after break in. do a compression test, make sure you do it correctly, and ask Howard about it too.

 

I agree on compression building as you break in the engine.

I dont think heatsoak is the problem unless its like 110 degrees where you live which its def not. Or you were doing endurance racing and your engine bay is piping hot which i doubt too since you're breaking in the engine lol.

Def do compression test anyway and/or call howard.

 

Hm ok, so I went out to check the FPR and when I turn the car to accessories, my FPR reads no fuel pressure. Do I need to have the jumper for the Diagnostic box or not?

I turn the car over and it starts turning maybe about 6-7 turns and then it finally turns over. With the car on though, the FPR reads the normal 38psi at idle.

Sent Howard an e-mail about the current problem.

 

you should see some fuel pressure when you turn the key on, what fuel pump are you running?

 

with key on, fuel pump should be priming and you should hear a buzz from the pump itself. I cant recall the specs for fuel pressure with KOEO. But the pressure should held nonetheless.

-AzEKnightz

 

I have a Supra fuel pump and yes I know that there should be fuel pressure with KOEO. When I was first setting up my fuel system/pressure, the car would hold fuel pressure in the KOEO position.

It can't be a problem with the FPR because it shows the pressure when the car is actually on. Also what I noticed is that when I turn off the car, usually the FPR would still show some pressure in the system but now when I turn the car off, it goes straight back to 0.

 

FPR should read about 7 psi higher with the key on engine off versus idle.

after shutting the engine off the fuel system should hold pressure for at least 15 minutes, if not then the check valve inside the pump isn't holding pressure or the FPR is leaking internally.

i would guess the pump primer not working could be an issue, if you try to start the engine while the pump is still trying to prime the system then i could foresee it flooding the still breaking in lower compression engine. did you rewire the pump at all?

 

Advance the cranking timing to 20 degrees L/20 degrees T and see what happens. It takes 5 minutes if you have a PFC Commander.

https://www.rx7club.com/showpost.php...4&postcount=34

 

Ben, I don't believe the pump has been re-wired at all.

arghx, I have a datalogit, so should I change anything in my base tune or should I follow the instructions and use the PFC that you linked me instructions to.

I'm wondering if it's my fuel pump or the FPR because the car was fine for the first 300 miles. The FPR showed fuel pressure when the car was turned to accessories and it would hold fuel pressure in the system after I shut the car off. Now that I'm having these troubles, the FPR shows 0psi when key is in the on position, and the fuel pressure drops straight to 0psi once the car is turned off.

 

I have been having the same issue for the last year. Last time it happened, I remembered this link and I adjusted the timing using the commander. It started more easily after that.

I probably should check fuel pressure but I have no way to check it.

Odd that it happened after a new engine on my car also. Never had hard start issues before that on the old engine.

 

I went ahead and drove the car today (it's been storming and I really don't want to take it in the rain) but there was a slight break in the storm. I went ahead and took a video of the "cold start" and then a "hot start" after driving the car about 8-9 miles and the car was fully warmed up just after casual driving.

What I noticed in the video is that when I turn my key to the on position, you can see the FPR blip up to the normal 38-40psi mark and then back down to zero.

I am uploading the videos from my phone now to youtube, so I will post them when they are ready. I haven't changed the timing yet.

 

Here is the cold start video, as you can see at 14 second of the video, the FPR blips to the 38-40psi when I turn the car to accessories. Seems to be 3-4 turns of the motor until it starts up.

http://www.youtube.com/watch?v=E5bhk-MhcAA

Here is the hot start video. This is a video of after driving 8-9 casual miles. Never going into boost and keeping the RPMs no higher than 4k. Takes about 3-4 tries before it barely catches and I can gas it to keep it alive.

http://www.youtube.com/watch?v=wEIv4V9_Yz4

 

Datalogit or Commander, it doesn't matter--same final result

My personal car doesn't hold pressure when I turn the key off. I know that's not a 'good' thing. It's not supposed to do that. But it still starts fine (not quite as quick as a 100% perfect stock car, but good enough). It's been like that for years and I honestly don't feel like figuring out what the problem is. It doesn't lean out under boost and has no signs of a 'real' fuel pressure problem.

advance the timing as I suggested and I'd give you at least a 50/50 shot of reducing the cranking times to an acceptable level.

 

So based on the thread you linked me to, we are going to advance "IGL Map" cells (N01,P09), (N02, P09), (N01, P10), and (N02, P10) to 20 in all four cells?

Then do the same in those cells for the "IGT Map" tab?

 

find those cells you mentioned and just put the number 20 in there, on both the IGL and IGT maps. there's nothing to it. use the Commander or DL software, it doesn't matter

 

 

Hmm, our values are very different

 

that map I posted is scaled up to almost 30psi bro

 

Ah lol, ok I'll go ahead and make the changes in those 4 cells in both tabs and try it out during Christmas break.

 

I had the exact symptoms on my Supra pump. Did a thread on this. Reason for my intermittent non-start and finally no start at all was the fuel pump sock being clogged.

 

Car was brought into a shop to fix a fuel pressure gauge. I told them about the starting issues and suggested that I wanted a compression test done. I contact Howard through e-mail and he said he's glad to help, but I do not want to disturb him during the holidays at the moment unless a serious problem does come up (low compression). I'll keep you guys updated.

 

did you ever try adjusting the cranking timing?