 do i need a fuel pump? |
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| nycchef |
 Apr 24 2006, 02:05 PM
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#1
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mechanical moron  Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None  |
73 914 1.7 (the one that tops out at 4000 rpm) now is idling @ 2000 rpm and dies every 15 minutes. einstein the mechanic thinks its the fuel pump now. i can hear it running. if i wait 10 minutes its starts again. does anyone know more than einstein and me. thanks
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| SirAndy |
Apr 24 2006, 02:36 PM
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(nycchef @ Apr 24 2006, 01:05 PM)  73 914 1.7 (the one that tops out at 4000 rpm) now is idling @ 2000 rpm and dies every 15 minutes. einstein the mechanic thinks its the fuel pump now. i can hear it running. if i wait 10 minutes its starts again. does anyone know more than einstein and me. thanks tell einstein to stop "guessing" and start using his brain ... (IMG:style_emoticons/default/rolleyes.gif) add a fuel pressure gauge and see if you got enough pressure. whatch and see if the pressure drops *before* your engine dies. if not, it's not the pump ... (IMG:style_emoticons/default/beerchug.gif) Andy |
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| nycchef |
Apr 24 2006, 03:03 PM
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mechanical moron Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None |
andy thanks for the reply do you know what the proper pressure is? so i can pass it on to einstein. also any one know a good 914 mechanic in nyc this one is about to have an accident just kidding maybe
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| Mueller |
Apr 24 2006, 03:09 PM
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914 Freak! Group: Members Posts: 17,146 Joined: 4-January 03 From: Antioch, CA Member No.: 87 Region Association: None 
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i'm too lazy to look for it...but you'll find the proper fuel pressure plus valuable tips and information on the D-jet here: Brad Anders D-Jet information overload site
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| SirAndy |
Apr 24 2006, 03:13 PM
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#5
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(nycchef @ Apr 24 2006, 02:03 PM) andy thanks for the reply do you know what the proper pressure is? so i can pass it on to einstein. also any one know a good 914 mechanic in nyc this one is about to have an accident just kidding maybe 28psi is minimum, 34psi is normal operating pressure ... here's a good article on the subject: http://www.rennlist.com/techarticles/djetronicfuel.htm (IMG:style_emoticons/default/smash.gif) Andy |
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| nycchef |
Apr 24 2006, 04:30 PM
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mechanical moron Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None |
andy thanks again will pass on to einstein you may well have kept him healthy for a few more days kidding rich
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| Dave_Darling |
Apr 25 2006, 02:18 AM
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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For D-jet systems (e.g., 1.7 or 2.0), the spec pressure is 2.0 Bar--2 atmospheres, or 29 PSI. 34 PSI would be significantly over operating pressure, resulting in an overly-rich mixture.
The high idle is almost certainly from a good-sized vacuum leak. --DD |
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| SirAndy |
Apr 25 2006, 10:00 AM
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#8
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Dave_Darling @ Apr 25 2006, 01:18 AM) 34 PSI would be significantly over operating pressure, resulting in an overly-rich mixture. well, what do you know, my Haynes manual says 34 psi for 1.7L D-Jet ... (IMG:style_emoticons/default/confused24.gif) Andy |
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| drewvw |
Apr 25 2006, 10:48 AM
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#9
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new england car guy Group: Members Posts: 1,631 Joined: 24-February 06 From: Boston, MA Member No.: 5,630 Region Association: North East States |
while we are on the subject: Dave you said that too much fuel pressure will cause and overly rich mixture. Besides that....are there any long term effects it can have on the fuel system if the pressure is too high for a long period of time? How much pressure can the system take before something catastrophic occurs? |
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| SirAndy |
Apr 25 2006, 11:01 PM
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#10
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Dave_Darling @ Apr 25 2006, 01:18 AM) For D-jet systems (e.g., 1.7 or 2.0), the spec pressure is 2.0 Bar--2 atmospheres, or 29 PSI. Haynes manual, page 39: pre '75 D-Jet = 2.4 kg/cm2 (bar) = 34 lb/in2 (psi) '75 D-Jet = 2.5 kg/cm2 (bar) = 35.7 lb/in2 (psi) (IMG:style_emoticons/default/confused24.gif) Andy |
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| SirAndy |
Apr 26 2006, 11:13 AM
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#11
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
i stand corrected! (IMG:style_emoticons/default/smile.gif) and dave was right ... (IMG:style_emoticons/default/beerchug.gif)
this is one of the times where the haynes manual can be "confusing". usually, you have a table with all the important numbers at the beginning of a chapter and then detailed descriptions of how to tackle certain tasks. but in case of the fuel pressure on the injectors, you actually have to read the fineprint in the article to get the right number ... (IMG:style_emoticons/default/rolleyes.gif) i usually use the haynes just for reference. i already know how to perform most of the tasks, so i mainly use it to look up torque values etc. i went to the table on page 39, looked up the fuel pressure for a pre '75 D-Jet and *thought* i was set. turns out, that value is only the pressure "at the pump", but not at the injectors. that number is buried in the fineprint of the "how to" article on page 42. 28.4 - 29.6 psi (1.99 - 2.07 bar) (IMG:style_emoticons/default/smash.gif) Andy |
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| Marlow |
Apr 26 2006, 01:03 PM
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Member Group: Members Posts: 311 Joined: 14-August 03 From: Manassas, VA Member No.: 1,027 |
QUOTE Besides that....are there any long term effects it can have on the fuel system if the pressure is too high for a long period of time? How much pressure can the system take before something catastrophic occurs? Too high of fuel pressure will cause a rich mixture that can wash the cylinder walls of oil resulting in increased wear. It can also blow-by your rings and end up diluting your oil; also resulting in increased wear. If you do determine that it's overly rich do an oil change as soon as possible. |
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| Dave_Darling |
Apr 26 2006, 07:59 PM
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#13
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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Too much for too long also increases the likelihood of leaks. The inejctors seem to not like high pressures for a long time. And I am told that the spray pattern starts to degrade over about 36 PSI.
--DD |
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