Hey guys.
Finished with the injectors today. Sounds and feels much better, although I haven't nailed it yet. Still needs some fine tuning.
The wierdest thing though, before I put everything back together, I checked the fuel system for leaks. Everything was good, the pressure stayed up for a couple hours before it was gone. Now that it's running, the pressure falls back in a couple minutes when shut down. There are no leaks.
If it was the valve in the fuel pump, wouldn't it have blead down when testing it? This isn't normal is it?
Thanks, Martin.

 

Glad to hear you got her runnin Martin. As for your question, I am not sure. But I, agree it doesn't sound normal.

 

hhhmmm cant tell you for sure. If it was me I would just forget about it unless it starts dropping while running. how long does it take to start? Like 1 turn over or 5 etc. ?
greg

 

Did you do any PROM work to reflect the change to 24lb injectors?

 

Martin: Mine does the same thing...sometimes the pressure stays up for quite a while and sometimes it drops right away. As far as I know it means the check valve is on it's way out. When I get the FP done next year I'll know for sure. But no, I don't think that's normal. I don't believe there's any leaks in the system (aside from the FP check valve) that would cause that. I would think that you would smell gas otherwise.

 

The car usually starts on the 4th or 5th crank.
As for the PROM, there's never been anthing done with it since I've owned the car. I have heard through the grapevine that 15th owner messed with it, so there's no telling what it is.
I have absolutely no knowledge with that stuff, so I'm at someone else's mercy or start buying aftermarket and hope for the best.
I guess that's one of reasons I went with the 24lb injectors, $500 cheaper then the 22's, figured I could put that money into some PROM work.
Gonna see about putting it on a diagnostic machine before Sunday and see what it's doing. There has been quite a few mods done and so far, the car hasn't reponded well.

 

Chris, is it possible that can effect the preformance? eg. fuel pressure dropping at higher rpm.

 

Well, considering my car has gotten slower since the spring with no real explanation, then I would think yes. This is my theory (note that it's a theory though)...I've had the pressure dropping problem, like you described, at least for the last 2 years. And it seems to be harder to start this year than last. I'm thinking that the fuel pump is starting to show signs of wear due to the reductions in my ET's at the track. I haven't changed anything performance wise since the spring yet my car is on average down 2-3 tenths as of the last two St.Thomas visits. I'm thinking if the FP is not operating to the best of it's capabilities then I'm gonna lose even more power at the top end, where the engine is demanding the most fuel. Bottom end torque and off the line my car seems to pull fine...I know top end is limited by the TPI setup as well but when pushed hard the performance seems to be lacking more than before.

At least that makes sense to me. I'm tired of wondering and worrying about it so I've commited to having the pump changed in the spring. I'm just gonna bite the bullet. I've got a Holley 255 FP sitting in my basement, I just need to get it put in.

 

I was affraid you gonna say that. It really sucks, cause I put a new fuel tank in last summer, but couldn't afford the pump at the time. It seemed to working ok.
Oh well, another winter project. Good time to do suspension work I guess...loll.
Thanks, Martin.

 

I hate to say it...but have fun!

 

Hey Chris. This morning I was playing around with the car and thought if run the engine, then pinch off the return line to the tank, shut it down, it'll give me a better idea what's going on. The fuel pressure went away like before. Did it twice.
This makes me think it's something at the engine. Since there are no leaks, I'm thinking regulator. Don't know for sure, but it's all tore down again. I'm gonna put the old diaghram from the stock regulator back in and see what it does.
I'll keep you posted.

 

All that work and the same. Damn.
Put the other diaphram in, no difference. Then pulled the 9th injector to see if it was leaking under pressure. Nodda.
Must be the FP valve after all.
Oh well, it was worth a shot.

 

Your mileage is gonna suck and the car is going to be kind of wacky until you have the injector constant changed.

 

Interesting troubleshooting...I never thought of pinching the return line. Are you sure you pinched the return line and not the feed line? Just checking...I wouldn't know which is which. It may not have been pinched hard enough either...Without wrecking the line I'm not sure if you can? Just guessing here though...good job regardless.

 

the return line is the smaller one and is rubber so you could pinch it off and not damage the line. most tool places have a tool that will do the trick. they look like a set of vice grips that are plastic.

martin if you did pinch off the return line right. and it still leaked down the only place the fuel could have gone is into the engine. with new injectors that should not be the case.

 

Hey guys. That's the part I can't figure out Scott. I've tested it 5 or 6 times in a row, without starting the engine and it still fires right up. I would think it'd be flooded if the injectors leak down?
I'm taking it in this morning, to go on a scanner ( won't tell me the fuel problem ) but the car seems to run fine, except at idle. Just wanna check to see what the a/f mixture is like. I'm not sure what kind of power it has at higher speeds. Bottom end has always been ok, but seat of pants dyno is hard to tell, up high. Guess Sunday will tell better.
I went to see the engine builder yesterday. He noticed to fuel pressure right away, without telling him about it. He says that will definitly effect the top end. It's problem that alot of drag cars have, that's why they look like there running so rich on the line. It's to get better fuel pressure down track.
Another surprising thing I found out talking to him. When he built my engine, we talked about putting in this certain Comp cam, but I said, you decide what will work best ( he's aways been right it the past ). So all along, I'm assuming there is a Comp cam in there. It's not. It's a Speed Pro cam.
Since the engine build was a trade and no money changed hands or invoices, he needs to have his supplier fax the part #, so I can get the specs. He can't remember...loll.
It's been quite a week.

 

Make sure you post the results. I definately want to hear about any and all findings as I have a similiar problem and don't want to do the FP if it's not needed.