I put a F.A.S.T ECM in my car and after the tuner tuned it, I noticed that it takes almost 10 seconds of cranking for the fuel pressure to read on the mechanical gauge I have. It only does this if the car has been sitting there for a while. Is this a hardware problem or could it have ssomething to do with software setting with in my program? It never did it with the stock ECM. THe pump is practically new. Its a Holley.

 

Does it prime for about 2 seconds (key on but not cranking)? If not, you need to hook up whatever wire primes the pump.

 

ya, I can hear the pump turn on for a few seconds but the fuelpressure gauge never moves. I could have sworn that with the stock ECM and TPI setup(mostly stock setup) that the gauge on the rail jumped to around 45 when I turned the key foward. Now, both the rail gauge and the cowl gauge dont budge until like 10 seconds of cranking. And this all started after the FAST install.

 

What all was changed, just the ecm and wiring or something else?

 

I ripped out the stock engine harness and stock ECM and replaced it with a new FAST engine harness and ECM. I had to wire up the stock fuel pump relay and coolant relay to the FAST engine harness but it was nothing major.

 

Did you change anything else? Fuel pump, regulator, etc?

How many times does it take to key it up (no crank) to get it to read on the gauge (key on, prime, key off, key on, prime, key off)?

 

I didnt change anything else that would be close to causing this problem. I havent just left the key turn on and waited to see how long it would take for the gauge to move. I will trey it tomororw morning. All I know is it takes 10 seconds of cranking before the car even starts. Im just worried that Im gonna ruin something from letting my engine rotate without oil pressure that long. Both my fuel pressure and oil pressure gauge ( both auto meter mechanical) sit still while cranking. the oil pressure starts to climbs just as the fuel pressure climbs up and then she starts. she also stalls out right after it starts and I have to refire it up and then shes good. it does refire right up too

 

My cars been sitting for over a week. I just keyed it up a couple of times:

1st time-about 30lbs
2nd time-about 38lbs but spiked to 45 while priming
subsequent times the same

Sounds like you have a problem with the cranking fuel table (either too fat or too lean). I had the same problem with mine, and it needs to be tweaked everytime a different size injector is used.

What size injectors are in there?

 

Im running 30lb SVO injectors. I just turned on my laptop and Im gonna see if I can get into my program tune and see if it lets me view tables even though the ECM is not connected to the laptop.

 

Update: The fuel pump will not prime right away if the car has been sitting overnight. Once the car has started, then the fuel pump will prime right up if I refire it. I even let the car sit for an hour or so and the fuel pump primed right up and the gauge went up. It just doesnt go it first thing in the morning or if the car has been sitting for a long time, over 8 hours. I cant get into my files until a new battery shows up for my laptop either.

 

When it sits overnite and doesn't prime, can you hear if the pump is coming on?

 

I went out to my car this morning and listened for the pump to turn on and it did as soon as I turned the key forward. the gauge also repsonded. That was the first time it did what it was suppose to do. In ther past, it never turned on. it did as I would be cranking for a few seconds and I wont be able to hear it prime while the car is crankiong. All Well. I am going to keep an eye on it and see if she acts up anymore. thanks for the help.

 

Try priming the pump until the gauge reads into the 30's (key on, no crank, key off, repeat). Then try and start it, and see if it still takes forever to start or starts right up, and we'll go from there.

 

the car will fire righ tup if the gauge read at least 30psi.. My problem is that the pump wasnt even turning on at all. It did for the first time this morning and the car fired right up. I guess the pump was giving my hell when I would go to start it after it sat all night. its weird. I wil keep an eye on it.

 

Sounds like the fuel pump relay is going bad.

 

I messed around with the contacts on the relay and it hasnt done it since.

 

I dont meen to steal your thread but i have been looking at the fast xfi system and was wondering how much it costs?

 

an XFI system is about 2100. nice system with good support.

DJ

 

Update on my problem. Its started again and it only started after I messed around with the relays on the firewall. I had the car off the other day and I could hear this weird noise coming from the relay. I put my hand on it and it was almost like the relay was surging or something. It wasnt quite clicking on and of but maybe like it was trying to and couldnt. It obviously is something electrical related and most likely is the cause of my fuel pump problem. It almost seems like maybe a terminal in the relay connector is loose or something and moving it around "fixes" it. And I bet that the weather(cold) in the morning has something to do with it as well. its like maybe the cold makes the contacts contract just a hair inside the relay and then it looses its contact with the actual relay. Once the weather warms up and the engine heat fills the engine compartment, it expands the contacts just that little bit it needs. I mean, thats all I can think of. I NEVER have the problem in the afternoon or after the car has run for a little while. Its just in the morning. I did inspect the contacts and terminals and they look fine to me. Anyone know if there is a replacement connector for the relays?

 

I really think this is your fuel pump relay on your firewall there. Mine went bad and thats exactly what it did. You wont get fuel pressure until the cranking engine builds oil pressure which then engages the pumps...about 10 seconds sounds right.

 

I swapped out relays with the fan relays and the problem was still there. And I am not running the factory engine harness and ECM anymore so I highly doubt that my oil pressure switch is still working in conjuction with the relays. I mean, it may be since its still screwed into the block and plugged in. I have no idea where the wires to it go since they are buired in the wire loom. I am not running a FAST ECU. But what you say does make sense since after cranking my engine for few, the mechanical oil pressure gauge will evenually start to build pressure and right after that, the fuel pressure gauge comes to life. A slow life, but it does go up to 43psi. Once it hits that, the engine fires.

 

I just put a bank to bank system in my car and its doing the exact same thing. Doesnt prime with the key on or until the key is in the crank position. After sitting over night it wont even do that for a while. Eventually it will start to prime in the crank position then start right up. Once the car has been warmed up it will start right back up anytime.

 

you probably already know this but the fast ecu simply supplys a switched ground to trigger the fp relay. there is provisions in the software to tell it how long to engage the fuel pump for in the key on position. I think it defaults to 4 or 5 seconds unless you change it. to test , you could disconect the fast trigger wire and ground the relay out manualy to see if the fp turns on and watch the fp gauge. your fuel pump could be getting tired or the relay going bad , bad /old connections in the wiring to the pump itself ect ect. you could always run power directly to the pump to eliminate everything but the pump for testing.

Doug

 

the sole problem with mone is the contacts in the relay. They are old and worn out. Sometimes my car wont do it for a few weeks. Then if I mess with the wires, it will do it.

 

UPDATE: well, after being off the road for a few monthes and other work being performed on the car, I am now ready to fire up my new engine and the fuel pump problem still exisit. It will not turn on when the key is turned foward. well it wont turn on about half the time.Other times it works perfect. I have now made the decision to rewire the fuel pump with a new harness kit. It should be simple enough to do but my only concern is how the pump will get the signal to prime for a few seconds and then stop if the engine isnt started. Like I said in a previous post, I am not sure if the oil pressure sensor is working or not since I ripped out the ECM and practically every single wire that came out of it. The wires coming off the oil pressure sensor go into that big wiring harness and dissapear from there. More then likley they go to the fuel pump relay and possible a 12v source but I am not sure. Anyway, how hard would it be to rewire the fuel pump with its own relay and fuse? My FAST ECU is set up to activate the fuel pump by grounding it, not by sending 12v to it.

 

have you tried a new fuel pump relay yet?

The FAST ecu fires the fuel pump by sending the GROUND to the relay. It will not supply enough current to fire a pump without a relay.

Doug

 

yes I have tried 3 relays anf it does the same thing. It has got to be a wiring problem at the relay. either worn out terminals or something. I would much rather rewire a whole new circuit with larger gauge wire. I am going to be runnng a large stereo and it gonna put a strain on my charging system so I would like to put larger gage wiring in there along with a new relay.

 

well its simple enough to wire a new fp relay and socket up. how is it wired up now? dont you have the fast fp wire going directly to the ground terminal on your fp relay? are you using a fast stand alone harness or are you using some kind of adaptor harness that plugs into the factory chevy harness?

dj

 

imusing the FAST stand alone harness. I had to do a little tweaking to the wiring on the fuel pump realy in order for it to work right with the - wire coming out of the FAST ECU. The shop I bought the system off of set me up with directions on how I had to switch around some of the wires on the relay. I did it rightbecause after I installed the setup, I took i tback to him so he could tune it and I had it double check my work and it all checked out. He also said that he had the same problem with the fuel pump not kicking in sometimes and he mentioned that one of the terminals in the realy was loose and he tweaked it a little but it was only a bandaid. In order to fix it right. I would have to get a new OEM stlye relay with new terminals inside of it. I have not yet found that so my my only fix is to rewire the circuit with larger gauge wire. I'll be fixing two things at once by doing that. my only problem is getting the pump wired so that it wil prime for a few seconds and then shut down of something like it is suppose to do. If I wire it independently, will it just stay on if the key is turned foward?

 

by independently do you mean you dont want to hook it to the fast ecu? for it to go on and off correctly you must control the fuel pump relay from the fast ecu . I guess you could wire it so it went on with the key but then it would bypass the 4 second prime deal. make sense? any decent auto parts store will have a generic relay and socket with pigtails. it would probably come with a cheap relay in it though. Bosch makes really nice relays.
DJ

"my only problem is getting the pump wired so that it wil prime for a few seconds and then shut down of something like it is suppose to do. If I wire it independently, will it just stay on if the key is turned foward?"

 

by independently, I mean not connected to any other wirng in the car except the FAST ECU's fuel pump output wire. I dont want it connected to the oil pressure or spliced into anything else along the way to the battery or anything. GM did some really crappy wiring on these cars. I think I seen something in the settings in the FAST ECU where I can control the prime time for the fuel pump. if so then im all set with that. I just have to rip out all the old fuel pump wires and relay wires and start all over with new larger gauge wire. At the same time. I can at least hide the relay somewhere under the dash or something and its one less realy that looks out of place under the hood. I will evenually do the same with the fans relay.

 

that will work. the fast has nothing to do with oil pressure gauge system at all. IF you are redoing the fp wiring then your should just buy 2 and do the fan at the same time. Main power to the fast ecu should go directly to the battery both positive and negitive. The smaller "switched" power wire should go to the fuse box so its activated by the ignition key.

You could Im sure fix the current setup to work but I dont blame you for wanting to rip it all out and start over . then you know what you have got.

DJ

 

That is exactly how it is wired right now. I wante dto rewire the entire car but I need to start with this fuel pump thing. this shouldnt be hard at right? I wired the entire FAST system and I didnt have any big issues so Im sure I can tackle this.I just dont want any surprises halfway into the job. SHould I just buy a pre assembled kit or should I buy the wiring and relays and stuff seperatly? Right after I do this, Iwill be takling the headlights. I plan on makeing a whole new headlight wiring harness like the one in the tech articles. Oh ya one wuick question, the fuel gauge wire can stay in the car right? its not spliced into the fuel pump harness or anything right? I only ask becasue I really dont want to pull my gauges out just to rewire one wire

 

the fuel gauge is totally seperate from the FAST ecu.

 

alright sounds good. Im gonna start looking for the parts I need to do this. There isnt any special conectors I need right? Do I have to drop the tank to do this or can I just splice into the connector located behind the rear seats on the outside of the car?

 

it all depends on how much wire you want to replace. personally I would locate the fuel pump wires as far forward as you can (under the hood if possible ) and splice into them by soldering the wires and use heat shrink wrap to seal it up. other than a good realy and socket you should only need wire and dont forget to fuse the hot feed.