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Does it have to be done at the rail? Can it be done before the fuel pump regulator? Thanks.
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You can fab a suitable fuel pressure gauge set up with a trip to the local hardware and automotive store if you have access to a donor fuel rail connection.
In the image below the male fitting and the female fitting are from the fuel rail of the donor car.
Randy
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Because what you need to test (per specs) is the regulated pressure.
The gauge is on a tee that is inserted inline, between the supply hose and the fuel rail. The regulator is connected at the other end of the rail and regulates the pressure by bleeding off the excess (above the specified values). Thus the gauge reads the pressure the the regulator "leaves in" the fuel rail. i.e., the "regulated" pressure.
My original post was hasty, and based on my intent to emphasize the "regulated" aspect of pressure testing, without giving the plumbing enough thought.
See Bentley 241-9 for LH 2.2 procedure and specs. ,Basically about 27 psi idling with regulator vac line connected—and 36psi with vac line removed and plugged (simulates throttle open/acceleration).
"K-Jet pressures and testing methods (below) don't apply to your LH FI system". I still stand by this comment. The method and DIY fitting linked shows a nice example of DIY work, but does not appear to allow the proper measurement of the two K-jet pressures: "Control" and "System".
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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Note the construction of a regulator:
A spring acts on a diaphragm resting against a port. This spring pressure seals the port until a equilibrium is reached between the spring pressure and the port pressure. The strength of the spring determines the regulated pressure.
This "port" is the connection to the fuel rail. After passing the diaphragm, fuel returns to the tank at atmospheric pressure.
Measurement can be made between the filter and the regulator, but not after, as the pressure would be about zero.
Lucid, I appreciate and respect your comments and suggestions. Please do not hesitate to continue to speculate in the future.
Goatman
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As I said in my edited reply above, I "shot from the lip" as they say—getting muddled by the original question: "Does it have to be done at the rail? Can it be done before the fuel pump regulator"
I knew the answer to the first question was "Yes", and sloppy thinking led me to think that "yes" ruled out a positive reply to the second question. When in fact the pressure IS measured "at the rail" AND "before the regulator".
My other comment (in my garbled reply above) was not meant as a put-down, but I felt obliged to point out that the your K-Jet (C.I.S.) system has little in common with the LH systems, so that Bonzo should not be looking for those high pressures. There is very little in K-Jet that can be offered in responses to LH posts.
The recommended K-Jet pressure testing method uses a special gauge set-up that allows reading those two pressures I mentioned (Control and System) by switching a valve, once the gauge hoses are connected. Unfortunately the gauge is getting scarce and is not cheap. The best price I know of is at JC Whitney—about $70 including shipping. (I paid $100 for mine from another source.)
Here is JC Whitney's page and item # Note that the gauge pictured is not the $59 K-Jet/CIS one.
I'd also recommend "Bosch Fuel Injection & Engine Management", published by Bentley. It's well written and explains K-Jet as well as the LH variations (including trouble shooting). It's only about $20+ and used ones can probably be found thru Amazon. The Bentley stock number is GFIB, ISBN 0-8376-0300-5
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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Thanks Bruce! I ordered the tester, seems like a good deal, esp. w/ the free shipping. Probably should have had one a long time ago, takes out the guesswork.
I've replaced a regulator before just guessing.
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"I ordered the tester, seems like a good deal, esp. w/ the free shipping."
What tester are you referring to? In my reply above to Goatman I was steering him to the special $59 K-Jet fuel pressure gauge set-up.
But the JC Whitney link does also show a simpler gauge for $34, which I assume will work for your LH system, using the supplied adapters. Is JCW offering free shipping?
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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I ordered the $59 K-Jet. I'll let you know how it is. They offered free shipping (I'm assuming this is a limited-time offer), but conservatively estimated delivery in something like 7-10 days (even though it's to go out within 24 hrs.). So I paid an extra $5 for 2-4 days expedited. Still not bad. I'm going to also look for the Bentley fuel manual, haven't gotten around to that. Thanks again for the advice.
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Sorry, but your car doesn't have K-Jet FI.
It has LH 2.2 so I doubt if you can use that gauge you ordered, at least not right out of the box. It will probably require various metric adapters, which are may be available but are nothing I'm familiar with. And you have no need for the more complex hose set-up with the 2-way valve.
Your best bet might be trying to resell it to someone that uses K-Jet (maybe on Turbobricks?), and getting the conventional FI gauge for about the same price as JCW but at Autozone or Pep Boys.
I didn't mean for you to get that gauge. My post with gauge info was directed to Goatman, who has K-Jet but from his comments (and added gauge port) seemed unaware of the K-Jet gauge requirements.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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FYI: I don't own any operational K-jetronics. That photo is of my 1983 B23F / M46 LH-Jetronic II setup in my 77' 264 GL Conversion.
My gauge port did save my arse after the Red Lobster. It worked all too well, for less then $5. I had purchased some various gauges previously for about $8 each.
I implore anyone that wants to check the pressure. Buy a few parts at the hardware store, and after that, it's all too easy install a gauge
Let me know if you need instructions. Maybe I should put together a kit and distribute them to Brickboarders in need. This "difficulty" seems to be a difficult fallacy to break.
With empathy,
Mr. Goat
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Hello Bonzo. That is a very good question and I'm glad that you asked it. In short, the answer to your question is yes.
Let me say that the fuel pressure is a very good indication of your fuel system condition.
I have posted a few times on this subject. See my post about Red Lobster.
http://www.brickboard.com/RWD/index.htm?id=1247784
This is a picture of the pressure port
http://www.brickboard.com/GALLERY/volvopic.htm?id=7443
Good Luck!!!
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