Fuel pressure-not rising 1 lb per lb of boost

[TR Custom Parts]

Ready to just leave this thing parked in the garage. According to some logs it looked like my 15 year old pump (around 20K miles or so) was not keeping up. Bought it from Kirban back in 85 and BELIEVE it was a Walbro 307.

Decided since the tank was 23 years old that I would just replace everything, new tank, sending unit, Racetronix Walbro 340 pump, new AC Delco fuel filter. Also put in a new Racetronix hot wire kit to replace the home made one I had. Hoses from sending unit to metal fuel lines was replaced, used submersible fuel line for the connection from the pump to the sending unit. Restriction was removed from the end of the pick up line, not the whole necked down part, just the end. Don't really think that should matter.

Getting 13.5 volts back at the pump at idle. Have the ground installed per Racetronix that goes to the rear bolt of the fuel strap and to the tank. Bare metal section with dielectric grease on the tank lip. Also put another ground from the tank lip to the frame itself. All grounds are to scraped bare metal.

Just assuming that the rubber line at the front of the frame is OK since the ones at the back of the car appeared to be fine but will check them out when I get the car up on the ramps.

Boost dialed in at 22 lbs with alky. Fuel pressure set at 43 lbs vacuum line off. Getting only around 59-60 lbs of pressure at full boost. Verfied with Power logger. Threw another fuel pressure regulator at it to take that out of the equation and same result. When boost comes up I am getting a high BLM spike which means the computer is trying to add fuel. This is what made me to decide to change the pump in the first place and there is absolutely no change. (anyone want to buy my old complete stock tank setup in CT??))

Once the initial BLM spike goes away and and the WB gets the correcton going everything looks fine except the fuel pressure numbers. Getting some minimal knock when I get on it but thinking that might be false knock with the downshift. STILL need to do a from a stop run with this thing but just haven't found the right opportunity.

Going to go thru the VortexBuicks checklist next and go from there. BTW, at a different time I had a 27 lb run and the fuel pressure was up to 65 lbs without any issues.

This is on a 32k mile car and all metal lines look like new at least from the outside. I did notice the bend right before the fuel filter looks like it might have been bent a bit too much but not to where I think it would be a problem.

 

[KevinB]

What's your voltage at wot? I saw where it was 13.5 at the pump at idle.

 

[TR Custom Parts]

Have to look at my pl logs think it was down to around 13 BUT from what I have read the PL gets the voltage from a different place? Voltage at the alternator where the hot wire is connected is usually higher???? Tempted to get a Kenne Bell Boostapump at this point or throw a Denso Supra pump in it like I originally was going to do.

Will take a pic of that line I though was bent a bit when I get the car up on the ramps. Busy week and not sure if I will get to it or not.

 

[KevinB]

It's still nice to know what the batt. voltage is doing going down the track. I was chasing a fuel pressure issue on a car I was working on recently. Ended up being the battery of all things. Car started fine, but the battery was always taking a huge charge.

Stupid question, but did you change the fuel filter after the fuel pump install?

 

[TR Custom Parts]

Yes, filter was replaced new AC Delco. Here is a pic of a snapshot, 12.9 was lowest voltage. Can try throwing in a spare battery I suppose. Fuel system is all new except for the fuel lines. Was getting almost 62 on this little burst but still low by 3 lbs. Maybe I am just worrying about nothing.

 

[KevinB]

One more little detail...what about the vac line going to the regulator? I've also seen cheaper or older vac lines fail causing a similar issue. Perhaps a boost leak at the vac port above the tb could cause this too (100% of the boost not reaching the regulator)....not sure but worth looking into.

 

[TR Custom Parts]

Replaced the factory setup with a length of heavy duty hose, zip tied at both ends.

 

[STP]

Sounds like a voltage issue to me...12.9V is not enough at WOT. Unless the PL is not reading accurately...

 

[Eric Stage I]

Mark,
In your other thread you posted the alky pressure, which looked like it was coming up really slow compared to boost. I think your fuel pressure may be fine since your A/F is good the rest of the run.

See what your alky pressure is when the boost first hits 22psi, then compare it to the alky pressure later in the run at the same boost.

 

[Louie L.]

Check the regulator diaphram. Just one more thing to eliminate.

 

[TR Custom Parts]

Check the regulator diaphram. Just one more thing to eliminate.

Had a Kirban full billet regulator on the car that I got last year, also had a new Accufab unit here that I put on and no difference. The alky, bumped up the initial turn on BUT chasing another issue as the alky isn't logging any more, just flat lining on the PL. Just up and stopped one day. I know pump is working since I also have a mechanical gauge.:smile: But that is another issue, Julio and I are trying to figure that one out.

Yeah, might be leaning towards a voltage issue, ever since I added my dual fans when they kick on you can sometimes feel the car struggle to keep idling for a fraction of a second. Have the Caspers harness that has the fans staged. Also have a fan on my trans cooler. Alternator is my original that I had rebuilt and chromed quite a few years ago.

 

[chevellejoe]

Yeah i second the voltage issue. My car at WOT reading from powerlogger is 14.1 volts.

 

[TurboDave]

Are you absolutely sure you even have an issue?? You're relying heavilly on a pressure transducer feeding info to the powerlogger.

If it were me, I'd get a good mechanical gauge that I could tape to the windshield/wiper arm and monitor it to verify whether or not the transducer is giving good or bad info.

 

[Otto J]

I doubt there is a real problem mark.If it really was down 5#s of FP it would be lean.
Both sensors could be off by a # or 2.
If your a/f ratio is good i would not worry.

 

[turbo nasty]

Have you checked the voltage and the FP connector by the tank vs. front of car?

 

[TurboBuRick]

I doubt there is a real problem mark.If it really was down 5#s of FP it would be lean.
Both sensors could be off by a # or 2.
If your a/f ratio is good i would not worry.

x2

 

[87GN_70GS]

60# injectors at 100% DC on pump gas only will exceed the capacity of a single 340, check the charts. But, it's only by a small margin. The pump's capacity is evenly balanced with the demand of 6 of 57# injectors (@ 100% DC) - or roughly the same as 60# inj @ 95% dc.

So I'm not surprised that WOT fuel pressure would be a tad short - except you have alky.

Can you log your inj duty cycle?

I would expect that the alky would drop inj DC% back quite a bit so that your fuel pressure would recover to a number that you would expect to see.

Can you increase alky delivery and monitor fuel press to see if it increases?

 

[Mike Licht]

try a different gauge, I will bet it will change. If the A/F is good so are you
ML

 

[TR Custom Parts]

try a different gauge, I will bet it will change. If the A/F is good so are you
ML

As far as fp gauges go, have hood mounted fuel pressure AND alky pressure. Then I have the power logger transducer for fuel and alky. Like I said the alky transducer is on the fritz right now. Only flatlining. Also put a decent fuel pressure gauge on the fuel rail when I had an issue with the hood gauge not matching the PL reading. Well the PL reading was exactly the same as the temporary gauge on the rail.

Got wondering about the fp when I saw a high BLM spike when the boost starting coming on and getting some minor knock. I will post a zip file of a run on here when I get home. Sure wish we could upload .dat files here.

With the alky system, I have a Metco fuel cell in the spare tire well, not sure if there is any issue there? Has a check valve up near the battery. I bumped the initial turnon a bit but haven't been able to tell if that is making a difference or not yet. So much traffic when I had the car out yesterday couldn't really get on it too much.

PS, I worry about everything.:biggrin:

 

[TR Custom Parts]

I doubt there is a real problem mark.If it really was down 5#s of FP it would be lean.
Both sensors could be off by a # or 2.
If your a/f ratio is good i would not worry.

How you looking appointment-wise? Pretty booked up??? Probably want to get the car in to you mid August.