fuel pressure

Thrty5thSC

Registered User
How long after you turn your car off should there be pressure at the fuel rail? What should my fuel pressure be with a stock pump?If i have red top injectors what is the lb rating on those?
joe
 
what is a good upgrade. i was thinking 36lb with a 190lph pump.
my mods are opened exaust with an s-port blower. soon i will have 75mm maf and 70mm t- body. the reason i asked about the line pressure is i'm getting detonation, only somtimes at wot and when i check to see if there is pressure after i shut it off there is just a little squirt. i think my pump is dieing. on my ranger if i push the valve on the rail in there is alot of pressure, even a couple of hours later. this is why i think my engine is starving for fuel, a couple of months ago i had no detonation, now i do. any help would be great. thanks fella's, and ladies.
joe
my book says fuel pressure should be 35-45 psi at idle, is this correct? i haven't checked it yet. my buddy has my pessure guage.
 
That setup is what I'm using.

Make sure the MAF has 36# sampling tube, or is cal'd to 36#.

To really make it work well, the EEC should be re-cal'd also. I use Rich's Tuner and a Dr. Fred file. There are other alternatives, but MN12 and Fred have been around and consistant for a looong time. ;)

Lee
 
Last edited:
i'm not upgrading right away. i know about matching the maf and injectors, right now i'm just concerned about detonation. what can eventually happen from detonation. what i'm asking is what just happened to my engine tonight? i was at wot tonight and amazingly giving a gsxr 600 a run for his money. when i smelled oil and now runs a little rough. no evidence of bad head gaskets but i do have oil all over my engine which apears to have come from the dip stick tube. i didn't lose oil pressure and the temp guage only went to the middle of the "n and o". no check engine light either. i haven't checked for codes though.
joe
 
Oil out the dipstick tube?

That's usually due to a clogged PCV valve.
The other (not good) possibility, with a lean condition, is a burnt valve or piston. I know from personal experience that the temp gauge doesn't tell you the actual temp INSIDE the engine. When my radiator let go, I was able to keep the temp inside the operating range but still ended up with 2 burnt pistons. You probably won't get a code with either of those possibilities.

Check the compression on all cylinders. Hope it's just the PCV.

Lee
 
Last edited:
i drove the car today and i think i hear a faint knock and it runs rough. not terrible just rough. could i have a bent rod or something? the pcv is ok. looks like i'll be installing another new engine. this will be #4 in two years. the other ones blew head gaskets from running hot. this one definitly has internal damage. sh@t.
joe
 
Knock or faint tapping sound?

That sound could be piston "slap". I know it's a real PIA on this setup, but check the compression. That'll at least eliminate valve or piston.
 
i'll do that. can't do it till saturday though. i work days and my buddy works nights and he's got the tools. what will tell me valve and what will tell me piston? i pulled the spark plugs on the pass. side, 2 and 3 were perfect, 1 was severly damaged. it looks like the picture in a repair manual, caused by detonation or pre-ignition. i did not check the driver side yet. i replaced the damaged plug and the car runs smooth again but the noise didn't change. if it's the piston can i put another one in with no machine work? as long as the cylander is ok? and how about a valve or valves? replace without machining? or is machine work inevitable? i don't mind putting money in it but i do my own work and i don't have time to wait for a machine shop. i may just longblock it again.
thanks for your help bro, i usualy don't need it but this is something i haven't experienced before.
thanks
joe
 
It all depends.

When you check the compression, you'll know if more than 1 cylinder's affected.
If the noise is piston slap, it's gonna deposit some aluminium on the cylinder wall. It can be honed off if it's not too bad.
A burnt valve may have pulled a bead of aluminium off the lip of the opening. If that's the case, you could go with bigger valves and have the heads re-cut.
I have seen both happen, so you'll have to pull the heads either way to inspect the damage. To check the cylinder walls, pulling the engine's the best way.

Hope it's minor.

Lee
 
thanks bro, i might just pull the head after the compression test. and find the bad news. i knew the fuel pump was weak but i hammerd her anyway. how does the saying go? you play you pay? i'll let you know what it is. i hope it's minor too.
thanks buddy for the help.
joe
 
Detonation could be caused by excessive oil in the IC and IC tubes, pretty common clean the IC and tubes out with solvent.. If you head detonation get out of it IMMEDIATELY. On forced induction engines it will kill the engine faster than you can hear it. Check ALL of the plugs. You should have about 30psi of fuel pressure at idle and it should add 1 pound per psi of boost.

Jeff
 
cause was low fuel pressure. the engine had 4k mi. on it i started to pull the blower off and the i/c is still pretty much dry. 17 psi of fuel pressure does seem to be the culprit. i get 10psi of instant boost and 16 psi max. everything is new, blower to struts. there is 15,000 bucks under my hood. damn fuel pump. 179000k should should have changed it. o well now it'll be even better. another chance for upgrades is one way to look at it.
joe:D
 
Last edited:
Back
Top