This is getting to be ridicules ..Nice day in Connecticut so I thought Id take a good long cruise before the show and salt hit. About 20 mile in the engine just shut off Nada. I have an inline fuel pressure gauge and it soon became apparent that there was no pressure. I went through the exact same scenario about a year and a half ago and it turned out to be the fuel pump the cutoff switch. The first one failed after about 30 miles so this time I got a different brand (which had all the same markings as the one I was replacing) and it has been good until now. I installed a jumper in the connector and the pump started right up and I continued on my way. Im running the pump through a relay so its not pulling any heavy amps through the switch so I have to assume that they are just cheap crap. I did some research and found that Holley has one that is a totally different design so maybe thats the way to go. Does anyone have any recommendation on what might be the best switch to use for the replacement?
Switches in general are really crappy quality anymore, even places that used to carry good ones, like NAPA now have junk. I go through a brake light switch on my roadster once a year and so does my Son on his T bucket. Just had to replace mine last week because it crapped out again. I have tried to buy a quality one but no one seems to carry one. Hope you find a good one. Don
I have on most of my cars in the past but there's still no guarantee that you wont have problems with fuel supply. I have this one set up with the electric pump and really don't want to redo it if i don't have to. If push comes to shove I'll just install a toggle controlled bypass on the pressure switch so if it craps out I'll be able to just flip the switch and go.
had a one year old new pump go bad, put an electric on and push it through the mech pump. no problems, no relay just a simple switch. Have to remember to turn off the switch.
Off chance that the switch your using isn't rated for the pressure. I'm assuming your using a oil pressure switch, it could be rated for 25-30 psi max. Had an issue at work with using and oil pressure switch for a reverse light, turns out the trans was pushing 40 psi on that port and the switch was only rated for 25 psi. The switch would only last about a month. How about the holley one: http://www.holley.com/12-810.asp
It's a Cole Hersee switch that's that's intended for that purpose but the max pressure for the switch is rated really close to what my oil pressure is and when its cold it could be exceeding it so that's a possibility. I was looking at the Holley switch but it looks like its pretty big in diameter and I'm not sure it will fit in oil tap at the back of the block without hitting the back of the intake. Anybody know what the diameter of the Holley unit is.
If you can't find another switch you can always use a couple of brass adapters to raise the switch about the intake. I had to do that on my SBC to use the autometer pro lite switch for my stock warning light. or
I don't know why I didn't remember this earlier. Some boat engine manufacturers, like Mercruiser and Volvo are now using electric fuel pumps instead of mechanical fuel pumps. Consequently, they also have an oil pressure switch the shuts off the fuel pump if the engine loses oil pressure or shuts off. The Mercruiser part number is 87-864252a01, and they sell for less than $30. They are pretty high quality because of being a marine item, and any MC dealer or Volvo Dealer should be able to fix you up with one. They are also very compact. If that Holley thing doesn't work out this might be a solution for you. Don
You're welcome, sorry I didn't think of it sooner. Here is a picture of what you get in the kit, as you can see, it isn't very big. Don't be afraid of the Made in Mexico thing, these have to be Coast Guard approved so they are held to a pretty high standard. Don
What brand switch are you using ? I have the same setup with an AC delco switch controlling the relay. At 2 psi it closes If you guys are having trouble , I'd like to change it now.
The first switch to fail was an A/C Delco part # D1847 which is the same as GM number 25037047. That one lasted about 500 miles. The second one was Cole Hersee #86267 which I'm told is no longer available which probably means they were having problems with it.
Over pressure along with pressure pulsations inherent in the system could be causing premature failure. An inline damper, (McMaster Carr), could help with the pulsations but still need a switch that can handle the cold oil pressures.
Wow, I'm surprised that factory (Delco) switch failed. I've seen those things with hundreds of thousands of miles on them and no problems. You might be right about being up against the pressure limit...
Maybe the fuel is eating the insides of the switch. Lots of rubber isn't safe around today's fuels and teh switches you're using weren't designed for fuel use. Edit: Sorry. My turkey hangover got the best of me.
There is no fuel coming in contact with the switch in any way.It's activated by engine oil pressure and controls power to the electric pump.
Why overcomplicate things? Just power the pump or relay from the ignition. Is this a carburettored car or injected? If carbs, only low pressure fuel involved and no need for fancy backup shutdown systems. If fuel injected and high fuel pressure involved, maybe a shutoff would be required. Lots of cars had electric pumps years ago, just came on with the ignition. Mart.
Me too. & that's the same one I have Unless the quality of newer manufacturing doesn't compare with older. According to the schematics I used, its normally open, the switch closes @2 psi and sends power out of it. Wonder if reconfigured to provide a ground would be easier on the switch? You would think if the switch failed due to over pressure it would stick closed. I had to use a 45* elbow on mine because it was too close to the headers. Could it be failing from heat ?
I bypassed the switch and got the car running and tested it with an ohm meeter.The Cole Hersee switch is a 3 terminal type. It has a common terminal that goes to the pump,a normally closed that goes to the starter solenoid to power the pump while cranking and a normally open terminal that goes to switched B+ that will close when the oil pressure exceeds 2 psi. With the engine not running I have continuity between the NC and common terminals which is correct. When I start the engine and pressure comes up I should have continuity between the NO and the common and I find that this does not always happen.Its very intermittent.If I rev the engine up and then let it come back to an idle which causes the oil pressure to change I can watch the switch drop out and I will loose continuity. The oil pressure gauge shows that the pressure never goes below 30 psi.Something is going with the switch and I thinking that cold oil pressure might have been great enough to distort the contacts in the switch and now when closed don't have sufficient pressure on them to maintain a good connection. When I install the new switch I'll cut the old one open and see in anything is obviously wrong.
Its not over complication, I wanted it set up so my or anybody's mom could drive it. No running motor = no fuel pump - pretty simple safety. Fuel pump starts @ 1.5 revolutions of engine caused by starter. I installed a momentary button just in case the fuel bowls need filled. Other than that its automatic. Some are a failsafe set up so that if you loose oil pressure your fuel pump stops and then the engine. Mine will do that too but not until its below 2 psi. The problem seems to be the switch, not the concept. Efi computers usually run the pump for a few seconds once key goes to on. Depending on what set up, the computer looks for oil pressure, or a similar switch ams the fuel pump relay.
Well hopefully the 3rd time is the charm. My new oil pressure safety switch just arrived.I did a lot of research and found that the switches that are being supplied to replace the OEM discontinued units are definitely sub-par.Apparently they are being manufactured overseas and are being sold by various venders as replacements for the Delco switches. I'm guessing that the replacement switches are made to low standards and from inferior materials and just not able to stand up to the high oil pressure on cold start for more a few cycles. The new switch is a totally different design and has a very high over-pressure tolerance,features gold plated contacts and is adjustable for off/on pressure. I'll give it a try and well see what happens. If you want to look at the specs here's a link. http://www.switchingssi.com/pressure-switch-polyimide-diaphragm-automotive.html
No matter how good your pump and switch are don't mean anything if the wires to and from aren't correct. I try to use better grade and heavier gauge wire and solder every connection and I think it's time and money well spent.
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