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FI to Carb swap question

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Old 07-09-07, 07:25 PM
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FI to Carb swap question

I've completed my install and went to fire up the car and............... nothing!

Fuel pump doesn't kick on, starter wont crank. Any ideas?
Are the starter and Fuel pump controlled by the ECU?
Am I going to have to rewire both the starter and fuel pump?

I've searched teh archives and I either can't use the search function properly or theres nothing on this subject. I figure someone here has done the swap so please help if you have any solutions.

Thanks in advance.
Old 07-09-07, 07:37 PM
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...I don't think carbs use electric fuel pumps... you've gotta use a mechanical pump.

But really, why not just use ITBs?

IIRC, the starter has nothing to do with the ECU... the ignition switch just gives the solenoid voltage, which fires the motor... although you have to do deal with the clutch safety switches.
Old 07-09-07, 07:40 PM
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Originally Posted by Valkyrie
...I don't think carbs use electric fuel pumps... you've gotta use a mechanical pump.


The car is an 88 N/A I swapped in a 13b 4 port BP with RB holley intake.
Old 07-09-07, 07:40 PM
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Well, you CAN use an electric fuel pump for carbs... but not the one on the RX-7.. its high pressure for EFI... you need a low pressure one.
Old 07-10-07, 06:20 AM
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When I did mine I had to jump the power wire that was hot when the key is on. Also had to ground the FP in the trunk area. A fuel pressure regulator is a must. I have a chrome holley one if you want it $30 plus shipping (if you get one make sure that it is the 4-9 since I believe that you need 6psi on the line to the carb.

As far as the starter I am not sure mine worked with the whole harness disconnected. I know it sounds stupid but make sure your starter is good.

Good luck,
Rey
Old 07-10-07, 10:54 AM
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Originally Posted by Jarroyo
I've completed my install and went to fire up the car and............... nothing!
Fuel pump doesn't kick on, starter wont crank. Any ideas?
The fuel pump is activated by the stock ECU when it senses the AFM start to open. You will need to rewire it to run from an IGN source. Make sure to use an inertia switch. Also you will need to replace it with a low pressure unit.

Are the starter and Fuel pump controlled by the ECU?
There is a starter cut relay, but that is uneffected by the ECU. Most likely you have damaged or disconnected the engine wiring harness.
Old 07-10-07, 01:17 PM
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Thanks guys, I already have installed an FPR. I guess I'll have to get wiring after I check the clutch switch.
Old 07-10-07, 01:19 PM
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Originally Posted by Jarroyo
Thanks guys, I already have installed an FPR. I guess I'll have to get wiring after I check the clutch switch.
an EFI FPR?
Old 07-10-07, 07:16 PM
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No its a carb regulator but I have a bypass set up on the system to compensate for the additional pressure. I got the fuel pump working and it holds pressure well at 5 psi with no problem. Now I' need to get the car to crank.
Old 07-10-07, 07:19 PM
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Originally Posted by Jarroyo
No its a carb regulator but I have a bypass set up on the system to compensate for the additional pressure. I got the fuel pump working and it holds pressure well at 5 psi with no problem. Now I' need to get the car to crank.
Should be as simple as the ignition switch, a relay and the starter..... If all three of those things are working.. the car will crank. I don't think the ECU has much in the way of controlling the starter. Unless you had a factory alarm, there might be a starter-kill type thing in place?
Old 07-10-07, 09:15 PM
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I went carb three years ago... It was easy...

I use a walbro 255 lph straight from the battery pole with a relay and a switch (good for anti theft LOL), a 650 cfm holley marine 4011 (discontinued model with floats on top) power valves removed, turbonetics blow thru, HKS racing bov, turbonetics deltagate, stiff 12-a turbo distributor, 1:1 aeromotive fpr 13301 model set to 7.5 psi, two msd blaster 2's two msd 6A's and a schwitzer t04B, custom exhaust manifold, 3" downpipe, flowmaster 3" inlet to dual 2.5" "Y", racing beat TII intake manifold... It sounds very quiet with the dual racing beat mufflers untill the wastegate does it's job since I have it spitting down to the ground... LOL

It is my daily driven car for work and everything else...

But I never had any troubles with my starter ... Not to mention it was automatic tranny when I started... Now it has a nice TII 5 speed in it... So let's say I did two swaps... LOL...
Old 07-10-07, 09:20 PM
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Got it to crank, but still no spark. I guess it's time to get out the wiring diagrams to see if I can get this electronic ignition to work. I would rather use the CAS & stock coils than go with a distibutor. So if anyone has any ideas throw em out there.

Thanks for all the help so far.
Old 07-10-07, 09:24 PM
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Did you remove any wires at all?
Old 07-10-07, 09:40 PM
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Does the tach needle move when you crank it??
Old 07-11-07, 11:28 AM
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Originally Posted by Angel Guard Racing Team
Did you remove any wires at all?
Only the engine harness that passes through the passenger side.


Originally Posted by Angel Guard Racing Team
Does the tach needle move when you crank it??
Didn't think to look, But probably no.
Old 09-14-07, 05:23 PM
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BTW when I said power valves removed.... I replaced the power valves with power valve plugs...


Check to see if the tach needle moves at all...
Old 09-14-07, 05:36 PM
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im doing this swap VERY soon - we need to make a sticky of this thread for everyone interested in the swap because there seems to be little knowledge out there about it - sorry for the thread jack


So even if you have a fuel pressure regulator, it wont stop the stock fuel pump from pumping too much psi of gas?
Old 09-14-07, 05:56 PM
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i've done this swap.. inside out back and forth, and have a kit forsale but pending at the moment.

you want to rewire your fuel pump to a low pressure unit, (whether its a holley or mallory, i prefer external pump, as internal pumps are questionable for me, i dont think there is a 8 psi pump anywhere that is internal), you want the mallory return style fuel pressure regulator, its the best thing for your carb and your pump, logically. to rewire, get a fuse link or whatever about 10 amp is fine unless u got problems blowing the sucker, have it as close as possible to the battery.run a wire into your driver side harness connect to a sw, the run a wire straight back to your fuel pump or where ever you mounted your pump (i had mine at the stock filter location, but you can do whatever is easier for you) and then just run a ground, and thats that.

then.. you want to get a distributor, you can use your coils, but it will not work with timing or timing advance. so i recommend getting the distributor setup, for simplicity reasons and timing advance or retard, you can get more power up high, now if you get this you can now dispose of ecu, and engine control harness, save accessories harness... (from passenger side)...

if you do want to keep your coils... you gotta pretty much make sure your ecu is in proper working order to fire in limp mode considering you have no tps, and shouldnt have omp either i think you cannot really remove all of your engine harness, gotta keep the grounds around.. i had one car run like this with no problems but lack of high end.. i mean like.. none what so ever after 6k rpm, i am sure its because timing cannot be adjusted or corrected (limp mode).. OR you can do a search in the first gen section to see how to rig up a chip to make it work normally, i read into it but felt it was just a hassel for a carb application, unless i got a first gen OR a big *** port to make that power.

makes engine bay look so clean, you want to splice the tach wire (yellow blue on the drivers side where t coil was) into the trailing coil of the dist setup, just hook that wire up to the ground side (correct me if im wrong.. may be positive.. i cant recall)


then make sure you remove or plug the omp, premix the hell out of it.. and you are technically done, make sure your starter is good

any high pressure fuel pump will either blow out your regulator eventually, or blow your carb out, OR blow it self out. its too stressful for the system.

Last edited by Mechanic; 09-14-07 at 06:01 PM.
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