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Old 10-02-2012, 06:57 PM
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jonygeorge jonygeorge is offline
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How to get fuel pump to run while cranking? Fuel Injection

(Calling all electrical experts)

Ok so i have my wagoneer fuel injected, I am running the fuel injection system out of a 1989 Mustang for the last 4 months and love it, only i have an eletrical gremlin i cannot figure out. I have bypassed the Fuel Pump wiring to the ECU and am just triggering a relay off of the Wagoneers wiring. When i am cranking the engine there is not power on the circuit that triggers the realy to run my fuel pump. I tried splicing off of the wire that engages my starter solenoid but this does not work because the power backfeeds to the starter relay and will turn my starter over whenever the ignition is on. The problem i have is i lose fuel pressure while cranking because my fuel pump will not run while cranking. I can still start the engine but i have to do short bursts of cranking to maintain some fuel pressure and usally have to attempt to start the Wagoneer 2-3 times before it will fire up. I am thinking i probably need to use a diode inline so that i can splice into the the wire that is hot while cranking to engage my fuel pump relay both while cranking and while in the normal run position without engaging my starter whenever the fuel pump circuit is hot, however i was wondering if anyone knows if there is a better way. Are there more than one wire(s) that are hot while the ignition is in the crank position on a 1988 grand wagoneer? If there is more than one hot wire to work with will i still have the backfeed problem engaging my starter when the fuel pump circuit is hot?

Is there a wire i can splice into that is hot both while the key is in the Run Position and Crank Position?.... If so help i cant find it.



Any advice would be appreciated.
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1988 Grand Wagoneer
Ford 460 w 429 heads Performer cam and Shorty Headers. Ford Fuel Injection out of a mustang. Natrual Gas Kit.
NV4500 Transmission NP205 Twin Stick T-case. Up and Running!

Last edited by jonygeorge : 10-02-2012 at 07:01 PM.
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Old 10-02-2012, 07:23 PM
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Tripwire Tripwire is offline
hey,does anyone here know how to.......
 
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Splice in parellel a momentary push button switch which will supply power while cranking, you should try to find a circuit that does both although....I tapped off my fusebox for the pump. Put a voltmeter on the empty spot and look at the voltmeter while turning the key thru the various key positions

As a plus its a great anti theft device
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Old 10-03-2012, 08:03 AM
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tgreese tgreese is offline
 
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Why can't you feed the fuel pump relay from both sources? You'd need to protect each wire to the FPR from back-feeding with a diode in each feed wire - so you don't activate crank in the run position, and vice-versa. Then the FPR would be powered in both crank and run.

You mention diodes in your post, so you've thought of this. Diodes are simple and easy - I would encourage you to use them. But you need a diode in both wires that feed the FPR.

Need more? Happy to elaborate.
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Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
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Last edited by tgreese : 10-03-2012 at 08:09 AM.
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Old 10-03-2012, 09:24 AM
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Carnuck Carnuck is offline
 
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I used a separate relay to engage the FPR while cranking. A lot of EFI systems (factory) have that built in already (2 second run on ignition bump)
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  #5  
Old 10-03-2012, 09:30 AM
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Quote:
Originally Posted by Carnuck
I used a separate relay to engage the FPR while cranking. A lot of EFI systems (factory) have that built in already (2 second run on ignition bump)

Unless you have a timer circuit, the relays just serve as a mechanical diodes. No need for the second relay - you can accomplish the same thing with 25c worth of silicon. And more reliably.
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Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk
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  #6  
Old 10-03-2012, 09:45 AM
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babywag babywag is offline
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Quote:
Originally Posted by jonygeorge

Is there a wire i can splice into that is hot both while the key is in the Run Position and Crank Position?.... If so help i cant find it.

The stock duraspark ignition modules wires.
One is hot while cranking, the other is hot in the run position.

Why bypass the fuel pump ecu wire? It's a good trigger wire for the relay.
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'88 GW (aka Babywag) and '90 GW (aka JUNKbucket) both fuel injected
1994 Caprice wagon
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  #7  
Old 10-04-2012, 05:14 AM
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jonygeorge jonygeorge is offline
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Quote:
Originally Posted by babywag
The stock duraspark ignition modules wires.
One is hot while cranking, the other is hot in the run position.

Why bypass the fuel pump ecu wire? It's a good trigger wire for the relay.

I like the idea of using the stock duraspark ignition modules wires...... I am assuming that is a 2nd hotwire during crank aside from the one i am using right now to trigger my starter relay?, however it was a while ago that i removed the stock ignition.... any idea of which pins these two wires are off of on the electrical bulkhead or which color they are on the 1988 wagoneer? I don't recall having found more than one hot wire on cranking when i originally did my wiring. I suppose i can hook up a test light and disconnect the bulkhead and try triggering every wire one by one to find another that is hot while cranking. If any one knows a quick way of locating this wire that would be great, and thanks for all the replys. If i am unsuccesful at this i will use the diodes, and yes i do plan on using the stock ecu to run my fuel pump eventually but havn't quite gotten to that. However i have another gremlin that i believe to be caused by my ecu to not getting power during crank and causing other issues aside from the the fuel pump issue on a circuit that is supposed to, so either way i need to create a solution and figure it out for both problems.

If i do indeed find the other hot crank wire from the stock duraspark ignition is this one isolated where it wont energize the other hot wire i am using to engage my starter relay? or will i still need to use a diode?

PS i did download the wiring diagrams on oljeep.com but is not clear to me which are hot during the vairous ingition key prositions.
__________________
1988 Grand Wagoneer
Ford 460 w 429 heads Performer cam and Shorty Headers. Ford Fuel Injection out of a mustang. Natrual Gas Kit.
NV4500 Transmission NP205 Twin Stick T-case. Up and Running!

Last edited by jonygeorge : 10-04-2012 at 05:59 AM.
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  #8  
Old 10-04-2012, 05:51 AM
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jonygeorge jonygeorge is offline
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Quote:
Originally Posted by tgreese
You mention diodes in your post, so you've thought of this. Diodes are simple and easy - I would encourage you to use them. But you need a diode in both wires that feed the FPR.

Need more? Happy to elaborate.

How do i know what size of diode to get? can a diode be purchased at radio shack for this application if so do i need one that is rated for a certain voltage and amperage that would be suited for this automotive application? Where should i buy diodes if not radio shack? ..... i know what a diode does but have no experience buying them or sizing them for an application. Thanks
__________________
1988 Grand Wagoneer
Ford 460 w 429 heads Performer cam and Shorty Headers. Ford Fuel Injection out of a mustang. Natrual Gas Kit.
NV4500 Transmission NP205 Twin Stick T-case. Up and Running!

Last edited by jonygeorge : 10-04-2012 at 06:03 AM.
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  #9  
Old 10-04-2012, 06:10 AM
jonygeorge's Avatar
jonygeorge jonygeorge is offline
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Quote:
Originally Posted by Tripwire
Splice in parellel a momentary push button switch which will supply power while cranking, you should try to find a circuit that does both although....I tapped off my fusebox for the pump. Put a voltmeter on the empty spot and look at the voltmeter while turning the key thru the various key positions

As a plus its a great anti theft device

The only reason i don't want to splice in a momentary run switch is my jeep is already similar to getting into a helicopter cocpit already. and i would like to simplify it so average joe can borrow my jeep without a manual on startup and shutdown proceadures. Between the additional 8 guages i have installed, the ECU Programming module and and the CNG Kit to run on natural gas, and the electrical gremlins mentioned in this thread I am the only one who can really drive the vehicle. At least as of this week i now do not have to manually turn my cooling fan on and off because i installed a temperature switch .. I am working on getting everything simplified so i can let a friend drive it or not have to watch my wife raise her eyebrow when she sees me flipping switches and guages. I have a friend i go hunting with that breaks out and sings "This is ground control to Major Tom" every time i take him for a ride. A good suggestion though Thank You!
__________________
1988 Grand Wagoneer
Ford 460 w 429 heads Performer cam and Shorty Headers. Ford Fuel Injection out of a mustang. Natrual Gas Kit.
NV4500 Transmission NP205 Twin Stick T-case. Up and Running!

Last edited by jonygeorge : 10-04-2012 at 06:23 AM.
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  #10  
Old 10-04-2012, 08:47 AM
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babywag babywag is offline
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Quote:
Originally Posted by jonygeorge
I like the idea of using the stock duraspark ignition modules wires...... I am assuming that is a 2nd hotwire during crank aside from the one i am using right now to trigger my starter relay?, however it was a while ago that i removed the stock ignition.... any idea of which pins these two wires are off of on the electrical bulkhead or which color they are on the 1988 wagoneer? I don't recall having found more than one hot wire on cranking when i originally did my wiring. I suppose i can hook up a test light and disconnect the bulkhead and try triggering every wire one by one to find another that is hot while cranking. If any one knows a quick way of locating this wire that would be great, and thanks for all the replys. If i am unsuccesful at this i will use the diodes, and yes i do plan on using the stock ecu to run my fuel pump eventually but havn't quite gotten to that. However i have another gremlin that i believe to be caused by my ecu to not getting power during crank and causing other issues aside from the the fuel pump issue on a circuit that is supposed to, so either way i need to create a solution and figure it out for both problems.

If i do indeed find the other hot crank wire from the stock duraspark ignition is this one isolated where it wont energize the other hot wire i am using to engage my starter relay? or will i still need to use a diode?

PS i did download the wiring diagrams on oljeep.com but is not clear to me which are hot during the vairous ingition key prositions.

They were(are) the 2 pin weatherpack connector that went to the module, one IIRC yellow and one green.

You should also utilize the ecm fuel pump pin/wire to energize a relay for the fuel pump.
That way you'll get the KOEO initial fuel pump run to build pressure before starting.
Download the ECM wiring diagram for a mustang and wire it like original.
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'88 GW (aka Babywag) and '90 GW (aka JUNKbucket) both fuel injected
1994 Caprice wagon
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  #11  
Old 10-04-2012, 10:36 AM
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tgreese tgreese is offline
 
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Quote:
Originally Posted by jonygeorge
How do i know what size of diode to get? can a diode be purchased at radio shack for this application if so do i need one that is rated for a certain voltage and amperage that would be suited for this automotive application? Where should i buy diodes if not radio shack? ..... i know what a diode does but have no experience buying them or sizing them for an application. Thanks

You understand that a diode is an electrical one-way valve?

There are fancy fast-recovery diodes and such as that, but you just want plain cheap rectifying diodes.

Diodes have two main rating numbers - voltage (peak inverse voltage, PIV) and current. For most components, you routinely spec double the peak operating value. So, for voltage, your peak could approach 20 V, so spec 50V minimum. For current, look at the current that your relay coil draws - that's what you want to power. Should be a fraction of an amp, so 2 amps would be fine.

It harms nothing to over-spec the diodes for your use - it just makes the diode larger and more expensive. So if you find a 250V 10A diode, that will work fine.

Here's an example - http://www.digikey.com/product-detai...ICT-ND/1228200 or here http://www.allelectronics.com/make-a.../50-PIV/1.html

Parts at Radieaux Shaque are always going to be more expensive than if you buy from somewhere like Digikey or Mouser or Allied, but the Shaque may have what you want on a peg.
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Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk

Last edited by tgreese : 10-05-2012 at 05:04 AM. Reason: relay, not solenoid
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  #12  
Old 10-06-2012, 08:25 AM
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mweath1 mweath1 is offline
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why not just splice inta a wire that is hot in on and cranking??? and skip all the diode junk there is a large black and red or pink wire under dash coming from column that satifies both on and crank, that is where i got the power to control my pcm for my edelbrock pro flo setup ill take a pic later on and post
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Old 10-07-2012, 09:37 AM
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jaber jaber is offline
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I didnt read all the posts, but have run into this on a 258 with a Howel setup. I used the hot leg of the coil to trigger the fuel pump relay in start. I dont have it in front of me, but could get details if they are wanted...
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Old 10-07-2012, 08:40 PM
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I'm sorry I didn't read all the posts, but isn't the ECU supposed to ground the fuel pump relay?
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