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-   -   S5 T2 fuel questions (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-t2-fuel-questions-643642/)

82transam 04-17-07 10:31 PM

S5 T2 fuel questions
 
Ok I've got a 90 Jspec T2 engine that I've swapped into a first gen. I'm running the stock ECU etc. Anyway I finally got the point where I can try to fire it up today, and no luck. It cranks and has leading spark (I'll have to look at my wiring to figure out the trailing) but doesn't seem to be getting fuel. The pump runs as it should, and there is plenty of fuel getting to the fuel rails, but no fuel comes out of the return line. Is this normal? It gets as far as the FPR on the secondary rail, but won't go back through the return line. Also, how can I tell if my injectors are firing? Is there a test connector somewhere I've overlooked? The engine will run for a few seconds if given starter fluid, so I'm pretty confident its solid enough to run, just need any help you guys can give with the fuel system...
Thanks
Sean

MaczPayne 04-17-07 11:22 PM

Tell me, where's your fuel pressure regulator located at? Secondary rail?

If so, run the feed to the middle of the primary rail, up to the secondaries, then from the secondary rail to the return.

82transam 04-18-07 09:45 AM

Yea, the FPR is on the secondary rail, there are no vaccum lines going to the primary. I'm not sure why everyone on here says that JDM engines run the fuel backward, the FPR is on the secondary on US engines as well isn't it? For some reason the fuel is stopping completely at the FPR, its not going back through the return line. I realize the FPR's job is to slow the flow in order to create the needed fuel pressure, but it shouldn't be stopping it completely right? Can the FPR just sieze up like that? If so how can I go about fixing it, I tried compressed air with no luck, and looking inside there everything looks pretty clean...

dregg100 04-18-07 09:49 AM

make sure your injectors are connected to the correct plugs. test the injector plug wires for power wile cranking too. as far as fuel not getting past the FPR, thats a good question.

RRTEC 04-18-07 10:22 AM

the j-spec hoses are reversed (fuel) so swap them around and drive it like you stole it.. The return line is in teh feed line position on the j-spec engine..

82transam 04-18-07 10:31 AM

So on the Jspec engines the feed goes into the FPR??

RRTEC 04-18-07 10:44 AM

Are you using the OEM (jspec) metal fuel lines?

Longshoe 04-18-07 10:49 AM

Should feed into the dampener and exit at the regulator. Are you sure you did not swap the lines at the rats nest near the fuel filter?

RRTEC 04-18-07 10:55 AM

That is what I am talking about. They are reversed compared to US spec at the hard metal lines right after teh Fuel filter.

82transam 04-18-07 11:57 AM

Yes I'm using the stock jdm lines, fuel rails, rats nest etc etc. I'll take a picture of the top of my engine later when I get home. I have the upper intake off so its all clearly visible. I have it running into the primary rail, then up to the secondary rail, which has the vaccum line going to it and then back to the tank...

RRTEC 04-18-07 01:16 PM

Reverse the lines entering the JDM rail. You are good to go then.

82transam 04-18-07 04:02 PM

Alright I'll give it a shot tomorrow when I have a chance to work on this thing again. Just seems odd that the FPR is last in line on the US cars, but first on the JDM ones...
Also, maybe a stupid question, but as my original post stated the fuel made its way all the way through the primary and secondary rail and stopped at the FPR, wouldn't it have at least tried to start? I mean there was fuel there at the injectors, shouldn't they have injected it into the engine? Oh well, I'll give it a shot and post back here once I do. Thanks guys!

82transam 04-19-07 01:42 PM

Ok, update. switch the fuel lines didn't help, now the fuel just stops at the FPR (the first thing it sees in this configuration) and doesn't go anywhere else. I've taken the fuel rail off, hooked its vaccum line up to my other car (a 12a that has plenty of vaccum) and the FPR does nothing. I've tried blowing air through the rail in all different directions, both with the vaccum hooked up and without. Nothing happens. In addition I took the fuel rail from a NA s5 engine that I have and tried the same tests and again nothing flows as it should.
I'm very sceptical that both fuel rails would be bad, but then I also wonder how the hell does the fuel get back to the tank??
As for the tailing problem I cleaned all the connections on the coils themselves (the eyelet connectors with the 7mm nuts holding them) and checked them with a test light. Oddly enough they have power going to them, however the trailing still doesn't fire. Using a test light doesn't yield any results when probing the leads coming from the computer (but it also doesn't on the leading, which in this case works) How do I go about testing the signal through these wires?
Lastly, I checked the injectors and the primarys are indeed clicking away when I crank it over, so now I'm really confused, I can get fuel to the injectors, and they click, why the hell wouldn't it fire up?
Sorry for the long post but I'm getting frustrated....

RRTEC 04-19-07 01:53 PM

What fuel pump are you using?

MaczPayne 04-19-07 01:53 PM

Not true, not all J-specs have reversed rails. Mine was ran the way I described, and my car fired up. If you aren't getting fuel returning to the lines, you may have a block in the secondary fuel rail.

As for the trailing coils, they don't fire during cranking. Atleast mine didn't.
If your fuel and spark are ruled out, check your timing.

82transam 04-19-07 02:36 PM

It's a FD fuel pump in a S5 pump hanger setup. I was playing around with the fuel rail some more and was actually able to get some compressed air to come out the return line, but it still won't allow fuel through. It just backs up at the FPR. I guess I'll run to my friends and borrow his timing light to make sure I have the CAS in properly, but I'm pretty sure I do...

82transam 04-19-07 06:14 PM

Yet another update, I borrowed a timing light and a fuel pressure gauge (both snap-on) from a mechanic I know, and my timing is dead on, and fuel pressure is 35psi. After cranking it over a few more times I pulled the plugs and they don't seem to be getting fuel. Yet the injectors are clicking, which is what confuses me. If there is enough fuel pressure, and the injectors seem to work shouldn't the engine be getting fuel regardless of whether the fuel is returning to the tank or not??
Is there something else I'm not thinking of like a out of adjustment TPS or bad AFM or something that could be causing all this?

Longshoe 04-20-07 10:13 AM

Was the fuel entering through the fpr or the pulsation dampener? Fuel needs to enter through the pulsation dampener and go through the rails then exit through the fuel pressure regulator then go back to the tank. I was not able to open my FPR via vaccume but from what I understand, they rarely fail. Jumper the fuel pump prime connector thing (whatever that yellow plug is called) and take off whatever fuel rail has the FPR on it and make sure to take the injectors out of the fuel rail too (leave the fuel hoses connected). Have another person turn the car to the on position. If you have the fuel lines connected correctly you should have gas shooting out of the fuel rail now.

If you do, then your injectors are not firing, or your flooded, low compression, etc. If you dont have fuel shooting out of your fuel rail then your lines are backwards if you do then shut the car off immediately. Now this may seem like kind of like an 'acid test' but im betting you have your lines backwards still. If you are not comfortable with this, then you could always take off your rails and run water through them to see if you have a blockage somewhere. As I understand it the FPR should always be the last thing the fuel passes through before going back to the fuel tank. Fuel cannot enter the fuel rails through the FPR... it must enter through the pulsation dampener.

edit TPS and AFM dont get the car started... but they do keep it running.

edit 2 where did you hook up the fuel pressure gauge at?

82transam 04-20-07 07:11 PM

Fuel is entering through the pulsation dampener (on the primary rail) and exiting out the FPR (on the secondary rail). I put the fuel pressure gauge inline between the hose coming from the firewall and the hardline on the rats nest. And yes, pulling the injectors out allows tons of fuel to spray everywhere, so the fuel is definatly making its way through the rails.
BTW thanks for confirming that my fuel system is indeed running correctly, i found it hard to believe that it would have to go backwards just because its a JDM engine...
Anyway, heres another update, i actually got it to run! However as soon as it starts it screms all the way to redline, so I'm gonna cheack the BAC and other major vaccum sources to make sure they aren't leaking. Something tells me the BAC is to blame, but I can't be sure just yet... I'll post updates as they unfold ;)
Thanks again everyone for all the help!

82transam 04-20-07 10:12 PM

2 Attachment(s)
Just took a closer look at the throttle body and I think that may be causing my problems, just want a second opinion before I go pulling the UIM again. See the attached pics, shouldn't the lower two butterflys (those are the secondaries correct) be closed all the way? Also, shouldn't the throttle mechanism be up against that stop (see red arrow)? In addition the front (towards front of car) TPS isn't touching anything, and the rearward one is half extended.
Could this be my high revving problem? Again I'm pretty sure it is, just looking for a second opinion.
Thanks

Longshoe 04-20-07 10:47 PM

It should-- those throttle blades are partially open. Something is causing the throttle linkage to jam open. See if you can see what is obstructing the linkage on both sides of the tb. I actually put an engine hanger for putting in the motor the wrong way and this caused the linkage to bind when trying to close. The throttle blades open like that could definately cause your problem.

MaczPayne 04-20-07 11:01 PM

Try adjusting your throttle cable length, if there is no blockage in the butterflies. You didn't happen to use the JDM Throttle cable bracket did you? I had the exact same problem, cept my car didn't rev up to redline, just had a 2k idle.

82transam 04-20-07 11:02 PM

Alright thats what I thought, I'll poke around tomorrow, theres probalby something stupid holding it open...
Thanks!

82transam 04-20-07 11:04 PM


Originally Posted by MaczPayne
Try adjusting your throttle cable length, if there is no blockage in the butterflies. You didn't happen to use the JDM Throttle cable bracket did you? I had the exact same problem, cept my car didn't rev up to redline, just had a 2k idle.

Yes it is the JDM bracket. Didn't know they were different. I'll take a look at that first...

MaczPayne 04-21-07 12:31 AM

Your throttle cable should have a tiny bit of slack when the throttle plates are closed. If the cables are taught and the throttles are open, that means you need adjusting.


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