jumper wire trick for powering the fuel pump. no run, failure. 74', was Ljet. now carbs Options

[rhodyguy]

the haynes current flow diagrams for 74' USA cars leaves me bewildered.

epic failure yesterday while trying to use the 'classic thread' version and eliminate using the + side of the coil to power the pump. made up a small harness to use the stock fuel pump circuit on the existing Ljet harness with the new cb pump. pump doesn't run with the key turned on. connected the pump (disconnected from the harness) to a battery with jumper wires and the pump is functional. does the ECU (brain) have the provision to power or ground the pump? if so, how do i get around that?

1. in the thread i note elliot is using a different pin on the relay board than the one used in andy's picture. is this due to differences in the harness? Ljet vs Djet?

2. in the 'classic' scotty914 makes mention of the pump relay being in the Ljet coil pack. now i'm lost. how does the power or grounding situation work now? i really don't want to go backwards using the coil to power the pump. i will, but prefer not to.

3. can someone verify the coil wires placement for me? 2 black ganged wires to #15(+)? grn condenser and red wire to #1(-)? do connections appear correct in the picture?

4. there is a small yellow wire (pictured) that connects on the relay board. what is its function and what is the correct location?

5. if i were to swap out the Ljet ignition harness for one off of a Djet system would that cure the problem?

carbs are plumbed and ready for the leak test, equal flow/linkage dial in and best lean idle adjustment. until i figure out what the pump problem is i will have to go back to using the coil to power the pump and not have to wait to get started with the tuning.

k

[rhodyguy]

edited thread to include ? #5.

[timothy_nd28]

Is the dual relay still installed? Also, where did you mount the rotary pump?

[rhodyguy]

pass side of the lower firewall for the pump. i'll take some pictures after while and post them. not quite ready to jack the car up and lay on concrete. was hoping to have some answers first. coil pack (i think) and a stray green wire. i hate figuring out what was done and undoing previous work.

[timothy_nd28]

Sure, there is a number of ways to wire this fuel pump. Ljet doesn't use the relay board to engage the fuel pump. This is done with the dual relay, AFM and the ignition switch. With that said, we can use the dual relay (if it is still installed) to power up your rotary fuel pump by changing a few wires. If you are set on using the relay board to power up the fuel pump, we can do this too. Totally up to you, fielder's choice. Option C (piggy back off the ignition coil) is the worse choice of all. I would not recommend this method, as extra current is being drawn thru the ignition switch and will cause premature failure.

[rhodyguy]

on my 73', prior to andy's instructions, i used the coil method and was less than pleased with the results. i want to use the fix thats the most effective. simple relay board or coil pack (presuming its functional). what cha' got for me?

[rhodyguy]

a cup of coffee later...if bridging a couple of points on the relay board is doable i think it would be the easiest.

[timothy_nd28]

There is a relay bolted to the battery tray, this may be the dual relay. Can you remove that one bolt, and take a picture of the underside so I can confirm this?

[timothy_nd28]

Ok, with terminal 3 grounded on the relay board, you should see 12vdc on pin 12 on the 12 pin connector (with the ignition switch turned on). I would verify this with your voltmeter. If this is the case, you need to chase down this wire on pin 12, and make sure it ties to your new fuel pump.

Also, you need that yellow wire tied to either terminal 2 or 4 for the starter to work.

[Tom]

Kevin,
In your second pic, you show a jumper to ground the pin for having the fuel pump relay work all the time, ( separate from any outside influence such as the ECU), and that is correct. However, you must have a power relay installed. Power relay is second back, fuel pump relay is third back from the front. Your pic shows no power relay.
Tom

[rhodyguy]

let me know if the pictures don't work for you. what may be the relay pack has been painted black at some point and i can find no #s.

[timothy_nd28]

Kevin,
In your second pic, you show a jumper to ground the pin for having the fuel pump relay work all the time, ( separate from any outside influence such as the ECU), and that is correct. However, you must have a power relay installed. Power relay is second back, fuel pump relay is third back from the front. Your pic shows no power relay.
Tom

good catch

[rhodyguy]

relay added. tim, terminals 2 or 4. 4 being next to the brown jumper or 2 on the right diagonally?

do the wires on the coil appear to be correct?


you guys are SO helpful. 914world ROCKS!!!

[timothy_nd28]

Going with the dual relay route, you would need to loose the yellow wire on 86a and replace it with the wire that goes to 86c.
Then tie the wire coming from 88d to your fuel pump.

[timothy_nd28]

relay added. tim, terminals 2 or 4. 4 being next to the brown jumper or 2 on the right diagonally?

Terminals 2 and 4 are the 2 most rear terminals.

[timothy_nd28]

[sixnotfour]

L jet only

[timothy_nd28]

Yep, leave the brown wire where it is, I assume the brown wire is tied to ground somewhere. And add the yellow wire to either terminal I circled in the above picture

[rhodyguy]

tim, the brown wire goes to the ground post forward and below the relay board and the small yellow is reconnected. you lost me. trying to sort this out looking at the current flow diagrams. which yellow wire? the one on the back of the dual relay?

86c moves to 86a. then tie (jump?) 88d to the supply wire for the fuel pump? i don't know where to physically locate those points. i'll never get there trying to read the haynes.

jeff, "Ljet only"? please expand a bit.

i think i'm real close with everyone's assistance.

[Tom]

Kevin,
If you are running carbs, you don't need any of the L-Jet stuff, do you? Power to fuel pump, power to coil, and power to starter. Sounds like the fuel pump issue is OK now, coil wires look OK to me, large yellow from pin 6 of 12 pin connector to starter and you should be good to go. Did you check with a volt meter that there is power at the coil + with the key to on? If you are removing all of the L-Jet stuff, you may need to run a wire (Black/red) from pin 7 of the 12 pin connector to the coil +.
Tom