Hobbs Switch for Electric Fuel Pump - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old May 13th, 06, 11:28 AM Thread Starter
LB1
Tech Team
 
Join Date: Jul 2005
Posts: 40
Hobbs Switch for Electric Fuel Pump

I've been attempting to install a holley pressure switch to shut down the electric fuel pump in the event of engine failure due to accidents, etc. I purchased the Holley pressure switch with three prongs and it doesn't seam to work properly. The egine is this 68 camaro is not stock. I'm guessing about a 1975 small block 350. Holley recommends running the pressure switch spliced on the starter wire. I can't get it to work.

I've tried every #@!$&### combination of wiring imaginable and no luck. I'm thinking of getting a Hobbs switch instead with two terminals. Will run a wire from the ignition terminal on the fuse box to one terminal and the other terminal to the positive side of the fuel pump. The wire running to the fuel pump will be fused with an 8 amp fuse. Should this work? I see hobbs makes a 2 terminal switch that opens at 10 -3o psi.
LB1 is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old May 13th, 06, 11:50 AM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Hobbs Switch for Electric Fuel Pump

You're putting this on oil pressure right?
Are you using a relay with your fuel pump?
The 3 wire switch will have a common terminal, a normally open terminal, and a normally closed terminal.

You DO need the 3 wire switch, otherwise you'll have no fuel when you're starting. Here's the tech info on part#12-810
http://www.holley.com/data/Products/...l/199R9680.pdf

The fuel pump wire (or the relay coil wire if you use a relay) is connected to the "C" terminal.

The "run wire" goes to the "NO" terminal. This connection will provide fuel pump power while the engine is running if you have oil pressure.

For the "NC" terminal, run a new wire to the starter. I would use the outer stud if your starter has one. This is the connection where the yellow wire attaches on a firstgen with stock wiring. This connection will provide power to the fuel pump ONLY when the key is turned to start.





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #3 of 10 (permalink) Old May 13th, 06, 12:44 PM Thread Starter
LB1
Tech Team
 
Join Date: Jul 2005
Posts: 40
Re: Hobbs Switch for Electric Fuel Pump

No relay being run Jim.Yes I'm running this off oil pressure and the PDF you provided is the part I have from Holley. I have three terminals on the starter solenoid (one has the battery + and a two red wire attached to it. I have another terminal with two red wire attached. I have a third terminal with a red wire with a white stripe that has been cut off and seems to have no purpose because the car runs fine without it? Help!

Bare with me Jim. It's tough to see where the wires lead. Headers in the way.

So you are suggesting that I cut the wire that runs from the starter key switch (12 gauge purple in the factory assembly manual wiring diagram), to the starter soleniod terminal, and hook it up to the NO terminal. Then, make up a second new wire and run it from the NC terminal on the pressure switch and run it to which terminal on the soleniod? The one where the battery is connected? And if so what do I do with the other end of the purple wire I cut that runs to the solenoid? I have made up a wire that runs from the common terminal to the fuel pump already (and fused it). I think my confusion lies in what the three posts on the solenoid do. I believe some run up to the alternator and one 10 gauge wire looks like it runs to a terminal block near the front headlights on the passenger side.

Any help would be greatly appreciated.
LB1 is offline  
 
post #4 of 10 (permalink) Old May 13th, 06, 12:56 PM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Hobbs Switch for Electric Fuel Pump

NONONO, stay far away from the purple wires on the solenoid!!!

The solenoid:
The large center terminal (where the battery cable comes in) is the power to start the car. Sometime people (and car companies) use this terminal to provide power to various things. Leave them alone.

The inner terminal (closest to the block, where the purple wire is) starts the car, it makes the starter motor turn. Leave it alone too.

The outer terminal was used on cars with points ignitions to provide a full 12 volts to the coil when starting for a hotter spark. This wire is not needed if you have electronic ignition, that's why it's cut off. If you look around the distributor, you'l hopefully find the other end.

You can use the outer terminal on the solenoid to provide start power to your fuel pump by connecting it to the "NC" terminal on the HOBBS Switch.

Connect the "NO" terminal to the IGN terminal on the fusebox.


Depending on how far you want to get into it, this could be a good opportunity to clean up some of the wiring. If you don't have A/C, it takes about 10 minutes to pull the pass side header and get some room to work. Also it's a good idea to run the fuel pump off a relay. Also, I'm afraid I'm not even positive what year and model car you are dealing with, tho my advise would apply to any gm car from the mid 60's thru the mid 70's.





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #5 of 10 (permalink) Old May 13th, 06, 01:29 PM Thread Starter
LB1
Tech Team
 
Join Date: Jul 2005
Posts: 40
Re: Hobbs Switch for Electric Fuel Pump

1968 Camaro coupe with no air conditioning Jim. Engine is about a 1975. I'll give that a try and let you know. The red wire with white stripe that I was refering to that was cut off seems to have no power though. It is attached to the outer post on the solenoid (nearest the header). I checked it with a volt meter while the car was running the other day.

What does the relay do and what should I ask for when I go to NAPA? It connects on the wire that runs from the c terminal to the + side of the fuel pump before or after the 8 amp fuse?

Once again your response is greatly appreciated Jim. I have restored this car from the junk heap and couldn't have done it without this web site. Good work!
LB1 is offline  
post #6 of 10 (permalink) Old May 13th, 06, 02:24 PM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Hobbs Switch for Electric Fuel Pump

Sorry took so long, my isp being hinky, second post today that I lost when I hit send...

So wut the heck was I typing half an hour ago?

68's I know at least, thatsa start. Stock, the starter had 3 wires. The big battery cable in the center, purple n the insode, and yellow on the outside. Anthing more, or different colors, didn't come that way.

The extra wires on the center terminal are probably to handle extra aftermarket loads, tho it escapes me why anyone would put them there rather than that nice handy horn relay.

Like I said before, you can run a wire from the NC terminal on the hobbs switch to the outer stud on the solenoid and get the fuel pump goin.

The relay lets you control a large load with a small switch. There were 2 recent posts that covered it pretty well, one about electric fans, the other about wiring up the neutral safety switch in a tko, find em and read em?

You haven't posted a lot, so I don't know your car. Some post lotsa stuff and pics, it seems I know their car's almost as well as they do. I'll look thru your posts, see what I can learn, but 25 in near a year ain't much.

At least for now, you can get the fuel pump going without a relay. It sounds like perhaps some of your wiring could use some attention, maybe.





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #7 of 10 (permalink) Old May 13th, 06, 02:31 PM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Hobbs Switch for Electric Fuel Pump

hmmm, interesting. seems half of your posts were electrical. Also, very odd, your first post, with pics of wires, wasn't answered at all. Did you figure those out? pic2 is a column shift neutral safety switch connector, 3 is the backup lights. not sure about 1 or 4, and it seems to have an awful lots of bulbs hanging around. Only ones I can think of on a 68 would be heater and radio illum, and high beam.





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #8 of 10 (permalink) Old May 13th, 06, 02:34 PM Thread Starter
LB1
Tech Team
 
Join Date: Jul 2005
Posts: 40
Re: Hobbs Switch for Electric Fuel Pump

Just tried your wiring suggestion and it works great. Thanks Jim. I owe you a beer if I ever meet you. Will get a relay this afternoon. You just saved me hours of work.
LB1 is offline  
post #9 of 10 (permalink) Old May 13th, 06, 02:40 PM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Hobbs Switch for Electric Fuel Pump

Glad I could help, gave me soemthing to do on a boring saturday after the car show i spent the last 2 days polishing for got cancelled due to weather.

If you're anywhere within a thousand miles of Billings Montana and free the weekend of July 8, you may buy me that beer!





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #10 of 10 (permalink) Old May 13th, 06, 03:34 PM Thread Starter
LB1
Tech Team
 
Join Date: Jul 2005
Posts: 40
Re: Hobbs Switch for Electric Fuel Pump

Turns out it had the wrong wiring harness with those early posts you were refering to. I ended up buying a new underdash harness and most problems went away. Had the engine rebuilt, body work done and painted and installed new interior. Changed it over to an SS clone with correct striping and an SS hood. Lots of money into it now. Looks good however.
I am within 1000 miles. Located up near Calgary, Alberta. Been to Billings a few times.
LB1 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
dumb question about clocking Mech Fuel Pump Brad74 Engine 6 Mar 21st, 06 07:10 PM
Running with the stock intank fuel pump... RegaMaro Performance 0 Mar 8th, 06 09:25 PM
Need help with stock fuel pump to AN fittings DanW Engine 11 Oct 2nd, 05 10:03 AM
fuel injection gas tank and pump 67ragtp Performance 0 Jan 12th, 05 02:47 PM
fuel pump question? hi-po327 Tech 2000 2 Jan 6th, 01 04:47 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome