d-jetronic fuel pressure regulator

mattillac · Post by **mattillac** » Wed Oct 27, 2004 12:22 pm

i have a 2.0 '75 914 with d-jet fi. everything is stock except the fuel pump
which i took from my 1977 280z. i hooked up a autometer fuel pressure
gauge to the cold start valve feed line from the fuel rail. i want to set the
pressure to about 33 psi, but no matter how i adjust the stock pressure
regulator, the pressure gauge always read the max pressure of 60psi.
aside from maybe an obstruction in my lines, is there anything else that could cause this? how can i test the regulator to see if it's bad? any help
will be appreciated.

Dave_Darling · Post by **Dave_Darling** » Wed Oct 27, 2004 3:42 pm

Try hooking the regulator up the other way around. If you hook them up backwards, I believe they act as a complete blockage.

--DD

mattillac · Post by **mattillac** » Wed Oct 27, 2004 5:29 pm

thats what i was thinking. i'll give it a try. thanks!!

raygreenwood · Post by **raygreenwood** » Thu Oct 28, 2004 7:47 am

Wait for a second. Is this a flow through type guage?...Meaning ...does the fuel flow to the cold start valve from the #1 and #2 side...into the gauge, then out of the gauge and into the #3 and $4 side? ie...is the gauge installed in place of the cold start valve with a "T"? If not and if you are dead ending at the gauge...you will read 60-70 psi all the time because it cuts the regulator out of the loop.
Also..be careful. 33 psi is about the max you want to go. At 35-36 psi, the injectors tend to get a little less reliable in fuel stream quality. Ray

mattillac · Post by **mattillac** » Thu Oct 28, 2004 8:18 am

at first i had the gauge T'ed in after the fuel rail, but it was reading max pressure. after looking up some more info, it seemed that the cold start valve fitting was the best place to put it. i do have it dead ending at the gauge right now, so i'll try putting a T there instead. thanks!

Dave_Darling · Post by **Dave_Darling** » Thu Oct 28, 2004 10:21 am

I think Ray's wording was just a little bit confusing. (Easy to do, because the ideas themselves are a little bit confusing!!)

The fuel system is a loop. The pump pressurizes the fuel, and feeds it into the fuel rails. The fuel then goes to the fuel pressure regulator, and from there gets dumped back into the tank. (This is a simplified view of course!!)

What you do not want is for this circuit to be blocked off completely. If, for instance, you put the gauge in place of the regulator, you will block the return of fuel to the gas tank and you'll read ~60 PSI.

If, however, you T the gauge into the circuit somewhere (there is usually a separate tap on at least one of the two fuel rails that you can use; on the 2.0 it feeds the cold start valve but on other 914s it may be plugged with a bolt) then you will see the correct pressure.

Stock fuel pressure for a D-jetronic system is specified at 29 PSI. You don't want to go too much higher or lower than that, even for "tuning" purposes. The injectors, as Ray alluded to, don't like it that much.

--DD

mattillac · Post by **mattillac** » Thu Oct 28, 2004 11:43 am

i'm going to try some/all of these tips on sunday. hopefully i'll get it all
sorted. i just hope there isn't a piece of crap blocking my fuel line somewhere. a while ago i found a big chunk of ??? blocking my fuel supply line in the tank. i had to take out the whole tank. no fun.

raygreenwood · Post by **raygreenwood** » Fri Oct 29, 2004 12:48 am

Dave said correctly...what I was trying to say....DOH! Dang I hate that when the coffee quits working

. I'll also cut back on those allergy drugs I have been smoking....uh I mean snorting.....uh.....takng!....yeah ! taking!...allergy....drugs. Later....

Ray

mattillac · Post by **mattillac** » Mon Nov 01, 2004 7:20 pm

what a suprise...i pinched off my supply line when i put my tank back in a while ago. fixed it and now the pressure gauge reads a steady 30-31 psi
after i adjusted it. i should have started there first...

albert · Post by **albert** » Sun Nov 07, 2004 7:51 pm

go to see autoatlanta.net and he have spécial pressure régulator for motor 1.7-1.8-2.0 ltrs porche 914 or vw 412 samething bosh the price is 145.00$ including the gage

Dave_Darling · Post by **Dave_Darling** » Mon Nov 08, 2004 9:52 am

The pressure regulator for the 1.8 is quite different from that used by the 1.7 and 2.0 injection system. The L-jet one from the 1.8 uses manifold vacuum as a reference, while the D-jet one from the 1.7/2.0 does not. Additionally, the D-jet one is adjustable while the L-jet one is not, at least not in stock form.

The website you reference is, umm... Incomplete.

Pelican Parts carries both types (D-jet, L-jet) of fuel pressure regulators for $60-70. You can buy a really b-tchin pressure gauge for the remaining $70...

--DD

raygreenwood · Post by **raygreenwood** » Tue Nov 09, 2004 2:03 pm

Yes Dave but remember...when you buy from AA...its for a Porsche...not a VW....AND you get that fabulous level of customer dis-service they are famous for thats GOT to be worth all the extra money in the world!

Ray