cypher85

Okay.. So I just finished up my head and intake swap; finally ready to turn it on and enjoy all of my hard work. Before I turn the key I hook up my fuel pressure gauge to make sure there is correct pressure. Well here is where the problems start. With the vacuum hose off I turn the car to the on position; fuel pressure builds to 40 then drops immediately to zero. Scratching my head I try this again with the same outcome. This did not make sense because two weeks before every thing was functioning fine. SOO I try to start it and it cranked a few times then stopped.. slowly turning the serpentine belt. I hydrolocked the motor. Pulling the spark plugs found 7 of the 8 plugs soaked in gas. Number 4 cylinder gushed out fuel when I pulled the plug and the dip stick smell test was overwhelmingly gas. I call the guys at FIC, where I bought my injectors, and they confirmed it to be stuck open injectors. Told me to send them in and I could opt to replace the bad ones for new ones for 18.50 an injector. This did not sit well with me because I just installed the superram and got everything tight.

My fuel pressure regulator had no leaks or smell from the vacuum line.

Because I didn't want to take off the superram I did some more research to find other possibilities. I came across a check for the electrical side of the problem. Unplugging the electrical connectors from the injectors and checking fuel pressure would tell me where the problem was isolated. So first I cranked the motor with the plugs out and distributor disconnected and the fuel pressure fuse pulled to get the remaining fuel out; re-installed the plugs. Before I put the fuel pump fuse back in I wanted to make sure the motor would still crank. Well it does thankfully and hopefully there is not a bent connecting rod in there.. probably not. So I plugged the fp fuse back in and disconnected the connectors from their respective injectors and turned the key to on; low and behold the pressure shot up to 40 and held it. I plugged the connectors back on the injectors to recreate the problem and it surfaced again. Now the only thing I changed other than the heads and intake was the tune. pcmforless(who did my initial tune) sent me an updated tune for the new parts and I burned it to my chip. I wonder if their tune could be the issue. I will be calling them tomorrow and emailing them the tune for them to check. If it is not that I will be checking my harness.

I then did a pressure test with the connectors off the injectors for leaks. 50 seconds after the key is turned to on the pressure leaks down to 30lbs from 40. Seven minutes after the start of the test it bleeds to 20lbs. I stopped the test after that because pressure seemed to stop bleeding. So in addition to whatever electrically is going on I may have a bad pump, leaky injector, check valve..

parts and length they have been on the car:

holly afpr-2 years
walbro 255L pump-2years
bosch 3 32lb injectors-2years

I have a used set of marren 30lb injectors that I can throw on too.

Is there any thing else that might be going on? Additional advice would be very much welcomed.

Mike

383vett

I commend you for methodically approaching the cause of the problem. It is unlikely that 7 or 8 injectors are bad, especially considering they are from FIC who has a great reputation. The pressure bleeding off from 40-30 in in 50 seconds is no big deal. My setup bleeds down to 0 in 5 seconds. A fpr not sealing totally or fuel pump check valve doing the same can result in pressure bleed down. I used to run a SuperRam so I know what it takes to remove injectors. I'm trying to figure out why the injectors are opening up when the connector is plugged in. Can you put the original chip back in to see if it floods the engine? That is what I would try at this time. Maybe the new chip somehow holds the injectors open.

cypher85

Thank you for your reply. Good to know about the pressure bleed. The stock chip was tossed 2 years ago when I got the chip from pcmforless. I do not have the tune they gave me then or I would re-burn that to my chip. The chip is the same as before just with an updated tune. I am thinking the updated tune is holding the injectors open. I initially was thinking about an issue with the harness; if somehow I damaged the wiring from the ecm to the injectors during the head and intake swap.. but that doesn't make sense.. even if the harness had issues the injector would have to be grounded and the wire connected would need to be short in order for the stuck open situation. This leads me to the tune. If after pcmforless takes a look at their tune and says there is nothing wrong with it.. I will be completely lost

383vett

The cause of your problem has to be electrical so it has to be either the ecm or the chip. Check the voltage going through the round injector connector. I believe the middle terminal is hot going to all cylinders, and the injectors fire when the ground circuit is completed. Those are the terminals on the outside of the connector. Turn the ignition on and use an ohmeter to see if the outer wires are grounded. This should not happen. I might be way off base with the positive and negative current going to the injectors, so wait until someone else chimes in. I'm going by memory since I don't have my fsm in front of me, and the memory is fading.

cypher85

I was wondering if I could do something like that. Basically I am looking for a condition which would only happen if the car was on right? If I get a reading with the car off then that tells me the computer is telling the injectors to open using your method. At least I think that is what you are telling me.

cypher85

In addition shouldn't I check for a short to ground on those wires with the computer disconnected? Also does anyone have access to a scan of the wire schematic? I do not have one.

ccrazor

Not sure of the wire colors on your vette but on earlier models power was supplied on pink/black and ground on light blue on one bank and light green on the other.. What 383vett is suggesting will show you if the wires that supply the ground to operate the injectors is there when you turn the ignition on without starting. It should not be.. Ohm meter from either green or blue to a good ground s/b infinity..

cypher85

Excellent! Thank you for clarifying. I will try in the morning. Thank you folks for your help. Today was a humbling experience for me

Cliff Harris

You need to disconnect ALL the injector connectors to measure for a short or voltage on the connector pins. Otherwise you have a connection through the injectors (which are low resistance). They are all connected in parallel.

You should see 12 volts on the pink/black wires with the ignition on. The ECM applies ground to the other wires (used to be light blue and light green, but may be different on your car). Those wires should not show any connection to ground. You might have a pinched wire, which would short it to ground. Check the blue and green wires for a connection to ground with everything disconnected (injectors and ECM).

The ECM pulses the injectors by applying a ground when it receives DRPs (Distributor Reference Pulses). The DRPs are used to synchronize the firing of the injectors to the rotation of the engine. The ignition module inside the distributor puts out DRPs any time the engine is rotating, whether cranking or running.

It's possible that the injector driver transistor inside the ECM is shorted (not likely -- they're pretty robust) and applying a ground all the time. Disconnect the harness at the ECM to check this.

STEVEN13

Not sure if your FPR is similar to a LT1-But if that goes bad it could dump fuel into the engine also.

Good luck,
Steve

bjankuski

cypher85

The wires that are on my car are black/green and black on the passenger side. And black/pink and black on the drivers side. With the ignition on the solid black wires read 12 volts each. With the ignition off the resistance reads 87 on the colored wires on all of them. With the ecm disconnected I read out of limits on the colored wires and 18 on just the passenger side black wires.. the ones that displayed 12v with the ignition on.

There are two connectors I cannot test. They are for number 7 and 2 injectors. They are disconnected but because of the plenum I cannot remove them fully from the injector to test them.

cypher85

Here is something interesting.. I found the fuse for inj 1 blown.. which controls 1,3,5,7

hooked073

I would look real hard for a pinched wire going to the injectors

cypher85

Found it.. the wire supplying power to #1 injector has shorted and burned apart. I will be getting new wire and heat shrink to solder it tomorrow. Found that because of that wire it was grounding all the other injectors open; I guess I should be thankful it is that instead of having to replace injectors. Much cheaper fix. Thank you everyone for your help!!

hooked073

that was my thinking that it had to be going to ground to keep the injectors open, Glad you found it

larryinalabama

Wires usually get pinched in some part of the Intake, causing multiple problems, both electrical as well as vacumn leaks.

cypher85

I got it started!! Now I have a very loud whistle vacuum leak! Sounds like a loud procharger.. on to the next issue. Time to investigate the superram.

383vett

Congrats, make sure you change your oil a couple of times.

cypher85

Do I have to change my filter?