Resolved 1G MFI relay or computer

[dikdiamond]

I tried to start my car but it acts like it has no gas, yet I have a 1/4 of a tank. I've checked the MPI fuse, and just for sake of argument my battery. I have a m/t computer along with 450 injectors and m/t FPR (my car is an a/t turbo). However what is stopping me from putting in this other computer, is that my current computer is non-turbo (which I didn't know until a week or so ago). I do know that using that other computer will change my timing settings and I'm not going to kill my newly-rebuilt engine (250 miles).

I haven't been driving it, only starting it up to let her idle a few minutes. Now it acts as if the computer is shot because I still have power and everything just no fuel. From I've looked up on the site, efi can cause this but so can a bad computer.

Any suggestions before I have it towed back to my mechanic? I need to have it towed if it is my computer, if not I can at least drive the 7 miles to the mechanic so he can re-set my timing after he changes my computer. If I could find an efi at a junkyard then I might be able to answer my own question, so far no luck.

 

[nates6969]

ok definitely a VERY bad idea to have a non turbo computer in your GSX. the maps in the nt computer are not designed for that much air flow and you will simply max them out causing a seriously lean condition. Not to mention the impedance of the 390 injectors w/ resistor pack are not the same as the n/t injectors and could fry the drivers in the ecu. it also doesnt have a knock board in the nt ecu.

if i were you, i would swap in the m/t computer and the 450 injectors that you have. this will have no adverse effects on the a/t as it is controlled by a different computer, the tcu.

I once had an ecu fry on my nt and it also caused the car to run like it had no fuel. would kick but not completely fire up. I came to the conclusion it was something with the fuel pump controller in the ecu, probably due to leaky caps. I hot wired the fuel pump to be always on and the car fired right up. it ran like a big bag of crap but it ran...replaced the ecu and it fired right up!

 

[dikdiamond]

Yes I do know it's not good, that's why I'm not driving it .

I'm not going to switch computers because of timings issues. I've been told by another member of the forum that the timing will change slightly,when going from non-turbo to turbo computer.

http://www.dsmtuners.com/forums/showthread.php?t=269790

So odds are it's the computer and not the efi?

 

[nates6969]

base timing is set by the crank angle sensor, not the ecu. chances are that guy who had messed up timing after an ecu swap, probably had it wrong to start with. and even if your base timing was off by a few degrees, under light cruise you wouldn't even know the difference.

just swap the ecu and injectors and you'll be set. get the timing checked afterwards if you want, chances are if its never been checked, it might be off anyways. you will do no harm by swaping the ecu to a correct turbo ecu just as long as you swap in the correct 450injecotrs with it. I have done a lot of ecu work and have had experience with all of them, so I can gaurentee you this.

 

[dikdiamond]

I'm supposed to take my car back to my mechanic at around 500 miles for an oil change and to check the timing (just got a top-end rebuild. he wants to make sure everything's ok).

I have a lot to learn. I didn't realize the CAS controlled the base timing. So everything should be ok then? Anything else to look for?

Edit: Any Wisemen want to chime in? Not that I disbelieve nates6969, I just prefer another opinion defending/denying is all

 

[Talesin]

Yes, the timing is controlled by the CAS (cam angle sensor, we don't have crank angle sensors on 1Gs, though the terms are used pretty interchangeably). You have to ground a connector on the firewall before you try to adjust the timing, as the ECU during normal operation will advance timing during idle so it can run leaner (ie: save gas) and generally futz around. Grounding that connector makes the ECU go 'hands off' so you can set the base timing to 5BTDC, which is what it assumes you're running on.

Honestly, I'm surprised that your car ran at all with the N/T ECU.. I didn't think that the pinouts for the connectors were even the same. The timing advance differences between the AT and MT ECUs is minor, mostly to compensate for the stock 390cc injectors and 13g turbo on the AT. If you have a set of 450s on, by all means swap in the MT.
Might have damaged your injectors though. Turbo DSMs use low-impedance injectors and have a seperate resistorpack on the firewall, while NAs use high-impedance injectors IIRC. Not sure if that'd cause an issue, thinking about it again though. Not like you were using NA injectors.

Just curious, how are you determining that it's not getting any fuel? Just cranking, but no ignition? Doesn't mean that the fuel pump isn't running. Personally, I'd change out the ECU first thing in the morning. It could be blown. The MPI relay (not efi relay) is located right next to it anyway, and isn't too hard to diagnose, given a battery and a multimeter.
Remember, our ECUs don't turn on the fuel pump until they can 'see' the engine turning (get rotation signal from the CAS) so sitting in the car with the key to ON won't let you listen for a running fuel pump, like a number of people have assumed.

 

[dikdiamond]

Well well well. I changed out the injectors and the computer and BAM starts right up! I'm letting her idle for a bit then I'm going to take her out for a spin (and clean her up). My idle surge problem has noticably disappeared also.

I Guess that ECU was the problem. Thanks to Talesin and nates6969 for helping me out I'll post if I have any problems or not

 

[nates6969]

pfff and you doubted me! haha...good to here that worked for ya...

 

[dikdiamond]

pfff and you doubted me! haha...good to here that worked for ya...

Hey now, in my defense I had two conflicting answers. One said yes (from the other thread) and you said no. I just wanted a majority rule before I tried it

Thanks again

 

[dikdiamond]

I have one gripe thus far. When starting up my car, it takes a few seconds longer than it did before. Almost sounds like it won't start, but it does so far.

Never does it if I just turn of the ignition then start it up a minute later. Less than an hour and it will do it again.

It might be nothing, just something I've noted so far.

 

[Talesin]

Welcome to hard-starting. Seems like just about every 1G out there with an upgraded FPR has it happen. How long do you have to wait? With the stock unit, I'd have to crank it for about 10-15 seconds first thing in the morning before it'd get going. Shut it off and start it, fires up almost instantly. It's considerably harder to start with the Aeromotive I have on there now.

You may need to replace the O-ring on your fuel pump, check for a stuck-open or slightly leaking injector, or replace your FPR... it's most likely that the fuel pressure that's supposed to be maintained in the fuel lines with the car turned off (21psi) is bleeding away somewhere. Though it might also be the result of a weak (undercharged or too-low rating) battery, too.

 

[nates6969]

my 1g only takes about a second and a half on a cold start and about a half second when warm. my fpr bleeds right off after a couple hours, I thank the fast starts to the walbro 255 for that. do you have an aftermarket fpr or pump? if so does the fpr have a gauge to watch the pressure build on startup?

 

[dikdiamond]

It takes about 10 seconds for mine to start. Before it was about a second and a half. I'm currently using the stock automatic FPR, which pushes about 6 psi more if I remember right. However I do have a FPR ordered, just a stock manual tranny version for now.

I had new grommets put on my injectors when I got my head rebuilt and I used them when changed to the 450's.

Same with the one under the fuel rail. Maybe I should take the fuel rail back off and reseat the injectors? I didn't notice any cracks in the injectors but would that cause them to leak or stick?

Would just rewiring my fuel pump help? I'm looking for diagrams of the fuel pump to find that o-ring.