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e170drvr's Avatar
 
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Yellow Relay Revisited.

I have been trying to figure out for the past several months why my fuel pumps come on with the ignition on and engine not running. It doesn't do it all the time. Finally wiggled the yellow relay with the ignition on and engine not running, turns out this is the problem. When I wiggle the relay the pumps come on. I know this has been discussed in length in several threads here, but does this relay have any other function than killing the pumps in a crash and over boost protection? I think I have read that it has several functions. Just wondering if this loose relay could be causing other problems? Car seems to run fine.

Eric
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Old 12-01-2009, 05:41 PM
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You could try spreading the split pins on the bottom so they fit tighter in the socket.
And some people have resoldered all the solder points on both circut boards inside the thing.

You can jump socket pins 30 and 87a on the bottom - pretty sure thats ground and the electro magnet coil wire leads inside it and go without it too.

All it does is what you mentioned along with causeing alot of frustration, tow charges and time wasted.
Old 12-01-2009, 06:14 PM
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Damn yellow relay from hell. Short between the terminals as Jim suggested (you may find that jumping between 87A and 87 also do the trick...I keep a jumper wire in the glove just for that purpose) and the pumps will run when you turn on the ignition. But the downside is that you will lose the overboost protection.
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Old 12-01-2009, 07:01 PM
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The wierd thing is that the car will start either way and run fine. Just some times the pumps will run with the ignition just one click, sometimes not. I think the normal behaviour is for the pumps to only run when the engine is actually cranking.
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Old 12-01-2009, 08:46 PM
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My 77 930 pumps turn on when I turn the ign. on. They both power on. Then I start the car. Starts every time. I think it is normal if you disconnect the lead on the CIS fuel distributor.

Robert
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Old 12-01-2009, 08:49 PM
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Hmmm, plug at the metering flap is connected? Wierd.... Oh well, starts every time, guess I can't complain too much.
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Old 12-01-2009, 08:56 PM
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...after 21 years alot of the electrical parts develop a personality.

could be your ignition switch or the switch at the metering plate is tired. there is also an adjustment for the metering arm and plate and their at rest postion in relation to that switch and it doesn't look fun to adjust.

i'm currently leaving the plug off the sensor plate switch so i can hear the pumps when i turn on the ignition and know it will start.
Old 12-01-2009, 09:19 PM
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Question on the over boost protection running with a 1 bar setting on e waste gate you have to ground it out. Any one know of the correct part number for a switch with a higher setting like maybe 1.1bar?
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Old 12-01-2009, 11:01 PM
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Quote:
Originally Posted by Ken911 View Post
Question on the over boost protection running with a 1 bar setting on e waste gate you have to ground it out. Any one know of the correct part number for a switch with a higher setting like maybe 1.1bar?
You're talking about the overboost sensor switch, with the single wire going to it (I presume)? Brand new, I think those are supposed to trip (interrupt ground) at something like 1.2 to 1.4 bar (foggy memory on that, sorry). I run 1.0 bar on my car and have yet to have an OB shutdown (yes my switch is working). If your car is prone to boost spikes, though, it might become a headache (as in face-in-dash syndrome). If yours is tripping, maybe it's just time for a new one?
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Old 12-02-2009, 11:23 AM
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Quote:
Originally Posted by JFairman View Post
...after 21 years alot of the electrical parts develop a personality.

i'm currently leaving the plug off the sensor plate switch so i can hear the pumps when i turn on the ignition and know it will start.
I replaced my yellow relay last year in the process of sorting out an issue that eventually I resolved at the fuse box connections for the pumps. The relay was a different manufacturer than the stock one, with a cool feature that the pumps will run for about .5 seconds each time I turn on the key. You hear this little "vrrrpp" as the pumps briefly run and shut back off, before engaging the starter. It's a comfort factor, saying that perhaps she'll start this time.
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Old 12-02-2009, 11:30 AM
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Where did you get this different yellow relay that has this function?

And yeah, a new overboost sensor doesn't shut off the fuel pumps until somewhere around 1.3 bar
I don't think anyone runs nearly that high a boost with street gas so it will probably only shut down the fuel pumps and throw you into seat belts if the wastegate hose or diaphram takes a crap.

I replaced that overboost sensor with a new one from pelican, (about $60) because the one on my car would shut things down at .95bar sometimes, and then it would take a few minutes to reset itself let you start the car.
I think the diaphram inside it was dried out and stiff and the spring it pushes against was fatigued and softened from age.

I've since heard you can buy an adjustable hobbs switch that will screw in the same for about half what the origonal sensor cost..
Old 12-02-2009, 12:21 PM
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[QUOTE=JFairman;5044140]Where did you get this different yellow relay that has this function?QUOTE]

Will have to check my receipts and stuff, as I can't remember. Internet search, the cheapest I could find most likely.
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Old 12-02-2009, 02:57 PM
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