A reasonable question re: Fuel pressure, Is it important Options

[76-914]

When setting fuel pressure, is there a recommended elevation to place the gage. Obviously, the reading changes as the gage is raised or lowered??
Any Guru's willing to comment on this???

[Brando]

If you are meaning that fuel pressure is changing on placement of the gauge (high or low) it should not change.

Ideally you tap in to the fuel rail with the removable bolt. It's fairly easy to see.

[SLITS]

If you can get a pressurized gauge to change pressures by elevation then you have a very special gauge indeed.

Now, if you are measuring barometric pressure then ..................................

And Brando ... the specified fuel pressure on a D-Jet / L-Jet is about 29.4 - 30 lbs. At 36 psig, you may override the injector solenoid.

[realred914]

well the Fi pressure is set to about 28 psi, any head pressure from gage hieght vartiation would be minimal percentage of the total.

i hook up my gage with a rubber hose right off the fuel rail port when I need to adjust and just let it lay at the same level as the injecotors more or less. even a couple feet of head presure variation would be a fraction of one psi. dont worry about it

[76-914]

OK, I'm going to take a video of it.Maybe I'll even be able to post it here. It is moving about 1-2 lbs as the rubber hose is raised and lowered. The pressure of water changes about.4 lbs per ft of elevation and it's specific weight is close to 8 lbs per gallon. Anyone know the weight of gasoline. I could extrapolate some kind of guess from that if I knew it. Thx

[Brando]

Thanks SLITS. I forget things.

realred914, are you sure you're not just seeing the needle bounce as the injectors fire? IIRC there's no dampener on the fuel system.

[SLITS]

OK, I'm going to take a video of it.Maybe I'll even be able to post it here. It is moving about 1-2 lbs as the rubber hose is raised and lowered. The pressure of water changes about.4 lbs per ft of elevation and it's specific weight is close to 8 lbs per gallon. Anyone know the weight of gasoline. I could extrapolate some kind of guess from that if I knew it. Thx

6.25 lbs/gal at 72 degrees F.

Put the joint out!

[SLITS]

Thanks SLITS. I forget things.

realred914, are you sure you're not just seeing the needle bounce as the injectors fire? IIRC there's no dampener on the fuel system.

You assdragger pilots forget a lot of things.

[Katmanken]

Got bubbles????

I bought one of those el cheapo Harbor Freight gages and realized that there is no way to purge air from it. So I looked and sure enough, real pressure gages (as used by mechanics and tv stars playing mechanics) have a bleeder.

Without an air purge bleeder, you might have an incompressible fluid compressing a compressible fluid and depending on how you move it, you might have different readings.

[realred914]

Thanks SLITS. I forget things.

realred914, are you sure you're not just seeing the needle bounce as the injectors fire? IIRC there's no dampener on the fuel system.

I have not seen much if any fluctiation when i run the motor, if you got good flow in the loop, variations are minimixed. at any rate I would think the gage should be at the same hieght as the fuel rail/regualtor, if you get a big change when you riase teh gage up in the air, then dont raise it up in the air, keep it low at teh same level as the fuel rail

the haynes manual for the D-jet says 28.4 to 29.6 psi so there is a big window of pressure to hit. the same book says that the L jet should be set to 35 +/- 1.4 psi again a big range. keep our gage at fuel rail level and you shoudl be a.o.k.

[76-914]

OK, here is what I found. When the gage was in a certain position it would barely leak at the barbed fitting connector. I hadn't noticed that earlier as I had a white shop towel beneath the gage. When I went to video this I noticed it; so you were right Ron. I did have a special gage. BTW I was testing with the ign on so the pump was not constantly running. This time I set it w/ the engine running. Guess what? ?Sabes que, miho? This is the first time I got it to idle at 950rpm. Go figure. I'm tempted to put those "new" injectors in, now.

[Brando]

"New" injectors or some well rebuilt ones may help.

Check out the prices for WitchHunter Performance.

He was able to rebuild the L-Jetronic injectors for my old BMW K75 for $50 per injector. He can also flow-match them so you know each cylinder is getting the same amount of fuel. From the factory they do not always flow the same and after time they can flow very different amounts.

And SLITS, I would probably, somehow maybe take offense to that comment, but I forgot already... Who are you again and what did you do with RON?

If ya come down this way sometime lemme know. Have a few (IMG:style_emoticons/default/beer3.gif) on me. (IMG:style_emoticons/default/beerchug.gif)

[realred914]

whitch hunter done my and tradsrad injectors, nice charts they provide with each injecter they clean and calibrate before and after reslluts of flow rate are proof.
recommend them.they ahd faster turnaround than i expected too. (IMG:style_emoticons/default/aktion035.gif) (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/smilie_pokal.gif)

[914Sixer]

New 1.8 injectors from Bosch are $50 or less depending on where you get them(Autohausaz.com). You have to look up 74 VW 412 with 1.8 motor but it is the same injector. Best to change out the hose though.

[76-914]

OK, I'm going to take a video of it.Maybe I'll even be able to post it here. It is moving about 1-2 lbs as the rubber hose is raised and lowered. The pressure of water changes about.4 lbs per ft of elevation and it's specific weight is close to 8 lbs per gallon. Anyone know the weight of gasoline. I could extrapolate some kind of guess from that if I knew it. Thx

6.25 lbs/gal at 72 degrees F.

Put the joint out!

I wasn't smoking a joint that time! (IMG:style_emoticons/default/lol-2.gif)