[s-cars] Fuel Pump Relay instructions (Long) Beta Version
Sean Douglas
quattro20v at telus.net
Tue Aug 3 21:52:02 EDT 2004
Wow Dave, that's some write up! Good job!
Sean, aka quattro20v
> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Dave Forgie
> Sent: Monday, August 02, 2004 9:31 AM
> To: s-cars
> Subject: [s-cars] Fuel Pump Relay instructions (Long) Beta Version
>
>
> Comments and Corrections welcomed. Some minor criticisms
> (sp?) tolerated. Alpha version will have photos and be a
> pdf. To be mounted at ??? Charlie? Jimmy??
>
>
> Adding a Relayed Power Connection to an UrS car (92-97) Fuel
> Pump (Beta version - Aug 2/04) Dave Forgie (UrS4boy) and Sean
> Douglas (quattro20v)
>
> Background (Interesting or boring, depending on your need for
> information)
>
> As opposed to some VAG products with two stage fuel pumps
> (transfer and high pressure), the UrS car has a single stage
> high pressure fuel pump located in the fuel tank. As
> provided by the factory, this pump receives power via a
> circuitous route: Power from the battery (under the rear
> seat) is fed forward to the central relay panel under the
> steering column. Turning the ignition on and starting the
> engine energizes relay No. 6 in that panel. This sends power
> from the relay via a green wire to Fuse No. 17, a 15 amp
> fuse, in the panel on the left end of the dash. From there
> power goes all the way back to the fuel pump in the trunk by
> the ski sack in a yellow striped green wire. Based on that
> route, the car started and 13.5 V or so at the battery, the
> voltage at the fuel pump is about 12.4 to 12.5 V, i.e. a loss
> of over one volt. This may not seem important but because the
> speed of the pump is related to the voltage, the fuel flow
> and pressure are also related to the voltage at the pump.
>
> While testing the fuel pump voltage while driving (via a
> tee-connection, 6 ft of wire, the zippered hole in the ski
> sack, appropriate spade connectors and a digital multimeter),
> I noted that voltage to the pump dropped (e.g. to 12.2 V)
> while driving and specifically even more so (down to 11.82 V)
> under wide open throttle (WOT). Sean some static testing of
> the fuel pressures under simulated boost (small compressor
> connected to the fuel pump regulator vacuum/boost port). He
> found that, with the engine off, at 11.75 volts (via a
> switched cable from the + post in the engine bay to the right
> side of Fuse 17), the boost/fuel pressures were as follows:
> 0/57,10/65,20/72, 28/80. However, since we are running RS2
> turbos and injectors and a new OEM 4.0 Bar (58 psig) fuel
> pressure regulator, the software wants more from the fuel
> pump, e.g. 0/58,10/68, 20/78, 28/86. So, since we were
> potentially down up to 6 psi of fuel pressure, it was clear
> that at least there was a possibility that the pinging we
> were experiencing under WOT was potentially related to low
> fuel pressures resulting from low voltage at the fuel pump.
>
> To test this more, with the engine off, Sean connected his
> switched static power lead directly to the battery and tested
> the simulated boost-controlled fuel pressures again. This
> resulted in 12.4 V to the fuel pump and boost/fuel pressures
> of 0/57, 10/65, 20/75 and 28/83. The point is that at the
> higher simulated boost pressures (20 and 28 psig ), the
> increased voltage (from 11.75 to 12.4 V) yielded an increase
> 3 psi. Although this was still 3 psi short of the required 78
> and 86 psig, respectively, it showed the potential that
> directly relaying the fuel pump to the battery would help us
> to "turbo charge" the fuel pump and get more flow and/or
> pressure. (NOTE: Dave Forgie talked to a technical rep at
> Bosch USA who said that low voltages are worse than higher
> voltages and that the fuel pump could handle up to 16 VDC so
> the regulated 13.5 V from an alternator should be "no problem").
>
> Based on the above, we (Sean and I) decided to find a way to
> directly relay the fuel pumps to the battery. As it turned
> out, it was relatively easy and quite cheap to do so. The
> results as you will see were quite worth the bother (in our opinion).
>
> The Install
>
> Before you can start an install like this, you need to
> understand how a relay works: A relay contains a solenoid
> (electromagnetic and armature) and contact points that are
> moved by the solenoid. There are typically four pins: two
> for a low current "trigger" signal (switched power and a
> ground), a high current line in and a high current line out.
> When the solenoidt is energized by the switched low current
> "trigger" signal, it pulls the closed which allows high
> current to flow from the power source to the point of power
> consumption. The trigger signal in this case is the yellow
> striped green wire that runs from Fuse 17 to the fuel pump
> (along with a brown ground from some source). The power
> source will be a connection to the battery and the point of
> consumption is the fuel pump.
>
> Parts List:
>
> 1 four pin 30 Amp relay, e.g. Bosch (relay holder and assorted pins
> optional)
> 8 ft of 14 or 12 gauge red wire (color is not critical but
> helpful) 8 ft of 14 or 12 gauge brown wire (for the new fuel
> pump ground) 8 ft of 18 or 22 gauge green wire (to extend the
> trigger signal switched
> wire)
> 8 ft of 18 or 22 gauge brown wire (to extend the trigger
> signal ground) 2, 1/4" insulated (covered) female spade
> connectors for 18 to 22 gauge wire 2, 1/4" insulated
> (covered) female spade connectors for 14 to 12 gauge wire 2,
> round terminal connectors, 1/4" hole, for 14 to 12 gauge wire
> 2, butt connectors, step down (22/18 to 14/16 gauge) (or
> soldering iron, solder and heat shrink) 1, heavy duty fuse
> holder complete with two 6" pig tails (12 or 14
> gauge)
> 1, 15 amp fuse for the fuse holder
> 6 feet of black corrugaged plastic wire loom (cover)
> 1 small plastic empty clean margarin tub c/w cover.
> electricians tape a sharp knife or box cutter wire cutters
> and strippers "W"-style connector crimpers. A straightened
> coat hanger Alternative 1: 2 butt connectors for 18 to 22
> gauge wire Alternative 2: 2, plastic "T" taps for 18 to 22 gauge wire
>
> The Procedure
>
> NOTE: We take no responsibility whatsoever for any damage
> that may or may not result from following this procedure
> either while performing the procedure or after its
> completion. If you do not have the confidence or skills to
> perform this procedure successfully and safely, then either
> do not attempt it or have a professional mechanic complete
> it. Before you start, read this all the way through to
> familiarize yourself with what you are going to be doing.
> Also note that there are two alternatives to the trigger wire layout.
>
> 1. Remove the rear seat bottom by removing the two large
> black Philips (x head) screws (and washers) from the front of
> the seat bottom. Store these screws in the margarin tub. 2.
> Inspect your battery. There should be plastic safety cover over the
> + terminal. If there is no cover, find one and install it before you
> complete finish this procedure. There should also be a clear
> plastic drain hose from the battery cap down to a rubber
> gromet in the floor. If this drain hose is missing then find
> one and install it before you complete the procedure. 3.
> Making sure that you have your car properly secured (in gear,
> emergency brake on, etc) AND you have the radio code, loosen
> the battery
> + terminal bolt and remove the + battery cable from the terminal. If
> the terminal is corroded, clean up the corrosion, e.g. with
> baking soda and a small amount of water and lots of cloths
> and/or paper towels (place the discarded cloths and/or towels
> in a plastic garbage bag, not in your car). 4. Loose the
> seat back by removing the two large shiny Philips (x head)
> screws (one on each side about the middle of the two outer passenger
> positions). Store these screws with the other seat screws in the
> margarin tub.
> 5. Open the trunk. Remove all the clutter that may be there
> and place it in a safe place out of your immediate work area.
> (You don't want to trip on it). You should be looking at only
> grey carpet. Its like a clean desk. You probably only get
> to see it once and a while. 6. Remove the carpet piece on the
> "hump" by pulling back the floor carpet at the corners and
> removing the two black quarter-sized discs (one at each side)
> and then remove the two discs at either side of the hump.
> Place all four discs in the margarin tub. Note how the
> carpet hooks over the threaded pins and then pull the hump
> piece off the pins and out of the car. Place in a safe
> place. Back at the car, you should be able to see a round
> flat black cover on the hump just to the right of the ski
> sack. This is the fuel pump cover plate. 7. Remove the fuel
> pump cover plate by removing the three small chrome Philips
> screws. Place these screws in the margarin tub. Gently pull
> up on the cover. Note how the factory routed the wires (in
> the plastic cover sheath). 8. Release the fuel pump wires by
> leaning or crawling into the trunk and noting the location
> and position of the fuel pump wiring plug. Remove the plug by
> gently prying the brown hook tab on the right side of the
> wiring plug and then lifting the plug slightly to the left
> (this should release the left hand hook tab - if it doesn't
> you'll need to gently pry that tab slightly as well). 9. Pull
> the plate and plug up away from the fuel pump and into the
> trunk so you have better access to the wiring. 10. Near the
> plug, carefully slit the plastic sheathing (DO NOT TOUCH OR
> CUT ANY OF THE WIRES) and open it up about 6 inches so you
> can see all four wires: a yellow striped green (the fuel pump
> power), a larger brown (fuel pump ground), a thin purple
> (fuel gauge sender power) and a thin brown (fuel sender
> ground). 11. Now the first "scary" part, boys and girls
> (insert Count Floyd howl here). You are going to cut the
> yellow striped green wire and the thicker brown wire, about
> 2.5" back from the plug. Do it, do it now. DO NOT CUT THE
> THIN PURPLE OR BROWN WIRES!! 12. At the long end of each of
> the cut wires, separately wrap the ends in a small clean
> piece of electricians tape (NOTE: This is for Alternate 2,
> for Alternate 1 you will be pulling these wires back). 13. At
> the short ends, strip the wire cover (being very careful not
> to cut ANY of the copper wire strands) sufficiently long for
> either the butt connector you are using or the twist, solder
> and heat wrap technique you will be using in a few minutes.
> 14. Approximately 2 inches outside of the rubber grommet
> carefully cut a small hole in the plastic sheath - DO NOT CUT
> ANY WIRES INSIDE. GO SLOW AND BE CAREFUL. 15. For Alternate
> 1, pull the yellow striped green wire and the thicker
> brown wire back through this hole in the sheath. Now,
> through the hole
> feed your new 14 or power cables through the sheath, towards
> the fuel pump plug. 16. Strip the appropriate length of wire
> cover from the ends of these power cables to make the
> appropriate butt connector or soldered joint.
> 17. Make the connections to the short plug wires. The red
> wire should
> be connected to the yellow striped green wire and the brown
> wire should be connected to the brown wire. NOTE: IF you are
> soldering, practise on some scrap wires until you can get a
> nice "Chrome" joint. ALSO, if you are soldering, remember to
> put your heat shrink tubing over the large wires and well way
> from the joint BEFORE you join the wires and start soldering.
> "D.oh!" is not part of this procedure. 18. If you are a
> happy with the connections, tuck all the wires in the split
> plastic sheath and tape the sheath with electricians tape.
> 19. If you are doing Alternative 1 for the trigger wires
> (the ones you pulled back out of the plastic sheath, strip
> the ends sufficiently for the 22-18 gauge butt connectors,
> strip the ends of your trigger wire extensions (18 gauge wire
> in green and brown) and connect green to green/yellow and
> brown to brown. 19. Place the long ends of the new power
> cables (and the trigger wire extensions in Alternative 1) in
> the black corrugated plastic wire loom, starting at the hole
> in the OEM plastic sheath. When you are done, tape the end
> of the new plastic wire loom to the OEM sheath (at the hole)
> with electricians tape. 20. If you have some, place a drop
> of Stabilant 22A contact enhancer on each of the four female
> plug connectors and reinstall the plug to the fuel pump. (It
> only goes on one way - it should go on easily - if not check
> the internal orientation and try again). Tuck the wire sheath
> into the same position it was in before you removed it
> (likely a kind of curl around the pump). 21. Reinstall the
> fuel pump access plate using the three small chrome Philips
> screws in the margarin tub. 22. Gently bend the wires in the
> corrugated plastic cover and instead of heading to the left
> side of the trunk (like the OEM sheath does), head them to
> the right side of the trunk, along the bottom edge of the
> trunk bulkhead. Don't go too far yet. 23. Now go into the
> back seat area, passenger side and gently pull the bottom
> corner of the seat back away from the trunk bulk head. Prop
> it away using something non-scratching (I used the wiring
> package). 24.Back in the trunk, tape the long end of the
> power cables (and trigger wire extensions in Alternative 1)
> and the plastic sheath to the end of a straightened coat
> hanger. About six inches from the right hand side of the
> hump and trunk bulkhead, there is a gap at the lower edge of
> the bulkhead. Shove the taped end of the coat hanger through
> this gap. If you have a helper have them grab the end of the
> coat hanger when it comes through into the passenger
> compartment. Gentley pull the wires into the back seat area.
> 25. Remove the tape from the wires and corrugated cover and
> gently route the wires along the bottom of the trunk bulkhead
> and through the gap on the trunk side and in the slight
> depression in the body on the passenger compartment side.
> Make sure you have enough wire to get to about 6 inches to
> the centre from the battery. 26. Replace the hump cover
> carpet, getting the appropriate bits over the threaded pins
> and adding the four plastic disc/hold downs from the margarin
> tub. 27. If you followed Alternative 1, skip down to Step
> 29, otherwise, you still need to extend the trigger wires to
> the relay. Start by going to the drivers side rear door area
> of the back seat. Find the yellow-striped green fuel pump
> power wire in one of the taped bundles and the brown fuel
> pump ground in another (smaller bundle). Note the location of
> these wires in relationship to the plastic wire tray that
> runs wires towards the battery. 28. With the appropriate
> color and gauge wires located, open up the two wire bundles
> and "T" tap the yellow-striped green fuel pump power and
> brown fuel pump ground and run the new "trigger" wire
> extensions (green and brown 18 gauge wires) over to the
> battery area in the plastic wire tray (Note: The covers on
> the tray open up so open them and lay the wires in the tray
> and then close the covers again). 29. Now you are almost
> there. Just the final connections and clean up: Play with a
> position for the final location of the relay. I chose the
> about the middle of the battery, attached to the bottom side
> of the plastic cable tray with a tie-wrap (NOT YET). 30.
> Make the connections from the trigger wires (either from
> Alternative 1 or Alternative 2) to the relay using the
> insulated 22 to 18 gauge 1/4" female spade connectors. Make
> sure you have the 18 gauge trigger wires and not the 14 gauge
> power cables. As you do this, trim the length of the wires,
> if they are too long for the position of the relay. The
> completed insulated female connectors should be attached to
> the male connectors on the low voltage side of the relay. On
> mine, this was spades 85 and 86. 31. With the new fuse
> holder empty (no fuse installed), connect the fuse holder to
> the + battery and terminal 30 on the relay using a ring
> connector on the battery end and an insulated 12 to 14 gauge
> 1/4" female spade connector at the relay end. Without
> putting a fuse in the fuse holder, put the ring connector
> under the battery cable bolt nut (take the nut right off,
> slip on the ring connector and then put the nut
> on) and attach the battery cable to the + battery post again
> (don't break the post by over torquing the nut). Attach the
> other end with the insulated spade connector to pin 30 of the
> relay. 32. Find a nice comfortable groove for the new power
> cables in the corrugated plastic sheath and then pull the
> corner of the seat back away from the bulkhead. Remove
> whatever you had proping the seat back away from the
> bulkhead. 33. Test the lengths of the new red fuel pump power
> cable to the position of the relay and the brown 14 gauge
> fuel pump ground cable directly to the negative terminal of
> the battery. Trim wire length, as appropriate. Leave a bit
> extra but not too much - the longer the wire, the more the
> voltage drop. 34. Make a 14 gauge insulated female spade
> connection on the end of the red power wire and connect to
> the power out terminal of the relay (87 on the relay I used).
> 35. Make a 14 gauge ring connection to the end of the 14
> gauge brown ground wire and attach to the negative terminal
> of the battery (remove the nut from the bolt, slip the new
> fuel pump ground over the bolt, add the nut and tighten
> (being careful not to overtighten). 36. Add a 15 amp fuse to
> fuse connector. Temporarily tape the relay to the side of
> the plastic cable tray. 37. Start the engine. If it doesn't
> start, you have a problem with one or more of your
> connections. Check and tighten connections. When the car
> starts and you are happy, stop the car and permanently mount
> the relay to the underside of the cable tray (I used a nylon
> tie wrap). 38. Make sure that the corrugated covered cables
> avoid touching the battery drain tube. Reinstall the two
> shiny Philips seat back screws. Reinstall the seat bottom
> with the large black Philips screws. 39. Enjoy.
>
> The end result was the fuel pump sees about 0.27 volts less
> than the battery at idle (before it was 1.0 V). Under load
> (WOT) before where I got 11.82 V, I now get 12.98 V. Has to
> help. In our case, the pinging problem seems to have gone
> away. We can't guarantee that your results will be the same
> (hey, they could be better!!)
>
> Dave F.
>
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