no start fuel delivery issue
Thread Starter
Racer
Joined: Jul 2007
Posts: 462
Likes: 21
From: Kansas City Missouri
no start fuel delivery issue
We just finished a rebuild and are having starting issues.
When we mist fuel into the TB is starts.
We have signal to all of the injectors, 42 psi of fuel pressure consistently, spark plugs are sparking, etc.
Just for reference, the two fuel lines that run into the fuel rail.....the fat one has pressure and fuel, but the smaller one is dry. Is that normal?
Would the cold start injector cause a no start?
Any thoughts on where to go from here? I can't imagine that all of the injectors are bad at once. That doesn't make sense and they are getting signal.
Thanks
When we mist fuel into the TB is starts.
We have signal to all of the injectors, 42 psi of fuel pressure consistently, spark plugs are sparking, etc.
Just for reference, the two fuel lines that run into the fuel rail.....the fat one has pressure and fuel, but the smaller one is dry. Is that normal?
Would the cold start injector cause a no start?
Any thoughts on where to go from here? I can't imagine that all of the injectors are bad at once. That doesn't make sense and they are getting signal.
Thanks
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
The injectors should have 12 volts on them. The ECM is the return and where your signal actually is which is the low end of the injector wiring. As I said the high side should have voltage on both wires of each injector while engine is not running. Check to see if a fuse blew. 
You can use a noid light also which will show the presence of voltage and the ECM functioning.
You can use a noid light also which will show the presence of voltage and the ECM functioning.
Last edited by pcolt94; Dec 18, 2010 at 08:25 PM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
As noted above ;12V or injector pulse?
Big difference
Cold start has no affect on the injector; just supplies extra fuel on a cold start like choke on carb car.
If the injectors were working, cranking engine long enough should get it to fire without the CSI
Big difference
Cold start has no affect on the injector; just supplies extra fuel on a cold start like choke on carb car.
If the injectors were working, cranking engine long enough should get it to fire without the CSI
Thread Starter
Racer
Joined: Jul 2007
Posts: 462
Likes: 21
From: Kansas City Missouri
When I said that there was a signal at the injectors, what I meant was to say that we used a noid light, which indicated that they were all functional.
I had oil pressure, fuel pressure, spark, everything..... just no start and it acted like it wasn't getting fuel. So, it is getting fuel to the rail, where the pressure gage is, but not down where it needs to, I guess. We even pulled a plug to see if there was any fuel spray upon cranking. My finger was a little moist, but not was you would expect.
When we misted fuel into the TB it fired and tried to start. Does anyone have a fuel flow chart that I can walk through? Not sure what else to do.
I had oil pressure, fuel pressure, spark, everything..... just no start and it acted like it wasn't getting fuel. So, it is getting fuel to the rail, where the pressure gage is, but not down where it needs to, I guess. We even pulled a plug to see if there was any fuel spray upon cranking. My finger was a little moist, but not was you would expect.
When we misted fuel into the TB it fired and tried to start. Does anyone have a fuel flow chart that I can walk through? Not sure what else to do.
Instructor
Joined: Jun 2009
Posts: 101
Likes: 1
The fuel will enter through the flow pipe and back out of the return pipe, so as the OP says there is no fuel from the other pipe, it sounds as though there is no circulation.
The flow pipe enters the fuel pressure regulator, which then fills the left hand rail up, then a crossover pipe fills the right hand rail up with fuel, then it returns to the tank via the return pipe, the pipe that the OP says is dry.
So, check that fuel pressure regulator.
Thread Starter
Racer
Joined: Jul 2007
Posts: 462
Likes: 21
From: Kansas City Missouri
Thanks guys and Merry Christmas.
Can I pull the FPR off without taking off the intake (plenum & runners)
How can I test the FPR?
When you say that it fills the left rail first, are you talking about the passengers side or the drivers? If the regulator was bad, would it still be showing 42 on the pressure gauge?
Could one of the cross over pipes be clogged? Would shooting air in there help?
Thanks again.
Can I pull the FPR off without taking off the intake (plenum & runners)
How can I test the FPR?
When you say that it fills the left rail first, are you talking about the passengers side or the drivers? If the regulator was bad, would it still be showing 42 on the pressure gauge?
Could one of the cross over pipes be clogged? Would shooting air in there help?
Thanks again.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Maybe but he has 42psi at the rail which should fire the engine if the injector are working
If the FPR is not working and venting fuel at the set point , you would expect higher pressure @ rail
Easy to get 50psi with stock pump and AFPR
If the FPR is not working and venting fuel at the set point , you would expect higher pressure @ rail
Easy to get 50psi with stock pump and AFPR
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Instructor
Joined: Jun 2009
Posts: 101
Likes: 1
If he had it at the rail, he'd get it back from the return pipe, but he says that pipe is dry.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Instructor
Joined: Jun 2009
Posts: 101
Likes: 1
Yeah, lol that's what I've already said, he needs to check his regulator. But it enters the reg first (before rails), which is why I suspect his rails are dry.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
So under your theory , how do you get pressure build up in the rails if rails are connected directly to tank?
What holds the pressure ?
On EFI fuel goes to rails first then the reg which holds pressure in the rails at the set point
His rails aren't dry ; he reports 42 psi pressure so he has fuel under pressure in the rails BEFORE the reg
Last edited by rodj; Dec 21, 2010 at 08:43 AM.
Team Owner
Joined: Jan 2003
Posts: 20,322
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From: Summerland B.C. Canada
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
It ain't going to the reg
If it was your engine wouldn't be running
The smaller 14mm fitting is return line FROM reg; connects to the steel line that runs on top of RH fuel rail to the reg
16mm supply fitting goes straight into the RH rail
Last edited by rodj; Dec 21, 2010 at 08:55 AM.
Instructor
Joined: Jun 2009
Posts: 101
Likes: 1
Go out to your '85 , undo the fuel SUPPLY line ( the larger 16mm fitting ) , confirm the fuel comes out of line when you turn the key on and then see where it fits.
It ain't going to the reg
If it was your engine wouldn't be running
The smaller 14mm fitting is return line FROM reg; connects to the steel line that runs on top of RH fuel rail to the reg
16mm supply fitting goes straight into the RH rail
It ain't going to the reg
If it was your engine wouldn't be running
The smaller 14mm fitting is return line FROM reg; connects to the steel line that runs on top of RH fuel rail to the reg
16mm supply fitting goes straight into the RH rail
I looked at the pdf, looks like I was wrong about it entering the reggy first.
But then why doesn't he get it firing on just four cylinders then?
Thread Starter
Racer
Joined: Jul 2007
Posts: 462
Likes: 21
From: Kansas City Missouri
ok, now that the holidays have had time to blow over, I was able to get up there today and work on the vette a little. We replaced the fuel pressure regulator, as it seemed to be stuck closed. The diaphram on the old one was getting warn anyways, so probably a good purchase. Now, we have a whole new set of issues.
The fuel pressure is now sporadic, where it was constant before. Sometimes it goes up to 40 psi when you cycle the key and other times it doesn't. Once it jumps up to 40 it immediately begins to bleed off. The fuel pump is getting signal. Do you think that the regulator could have caused the pressure gauge to read falsely high? Do you think my fuel pump is now going out? It still won't start btw. The pressure gauge seems to stay at 40 while cranking, but then bleed off once done, whether the key is on or off.
The fuel pressure is now sporadic, where it was constant before. Sometimes it goes up to 40 psi when you cycle the key and other times it doesn't. Once it jumps up to 40 it immediately begins to bleed off. The fuel pump is getting signal. Do you think that the regulator could have caused the pressure gauge to read falsely high? Do you think my fuel pump is now going out? It still won't start btw. The pressure gauge seems to stay at 40 while cranking, but then bleed off once done, whether the key is on or off.
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Suggest taking the pulsator off and replacing it with a short piece of hose. These like to leak and cause pressure problems.
The pulsator is on the fuel pump assembly, between the fuel pump and the outlet tube.
The pulsator is on the fuel pump assembly, between the fuel pump and the outlet tube.