Fuel Pump, Filter and lines

[POZE]

Is the oil switch a safety switch or back up for a bad FP relay?

[Six_Shooter]

Is the oil switch a safety switch or back up for a bad FP relay?

It depends on how you wire it.

[POZE]

Hmm How would you wire it to be a safety switch? It would be easy for me to make a change now. I wired it like GM wiring diagram. 92 s-10 2.5

[1project2many]

GM wiring puts the switch in parallel which means either the switch or the relay can operate the pump. If you wire the switch in series then the pump will not work unless the relay is closed and there is oil pressure too.

[POZE]

Would that change cranking time much or at all ? That would make a good fuel cut off if you lost oil pressure.

The fuel pump relay is powered by the ECM unlike most circuits that are ground controlled. This was done because of a chance of the relay control wire being grounded during an accident.

[EagleMark]

The fuel pump relay is turned on by ECM but not powered by it, if it is then check your wiring.

[1project2many]

The relay coil is powered by the ecm but the contacts are battery powered. Cranking time will depend on the engine's ability to build oil pressure and possibly on how quickly the fuel system can purge air as you will lose the two second "prime" function built into the ecm. An advantage is the engine will never start without some oil pressure. Of course additional starter wear, battery draw, and generator / alternator heat may become issues. Everything is a tradeoff. Now if you want to get really creative you could use the starter "crank" circuit to energize a bypass relay which allows the fuel pump to engage during cranking but reverts back to the oil pressure safety circuit after the engine is running. Toyota actually uses a dual coil relay in the pre 95 trucks for a similar purpose.

[POZE]

I was just saying the FP relay magnetic coil is powered by the ECM. In most circuits the ECM controls the ground.

[1project2many]

Gotcha. That circuit is commonly misunderstood in the world of internet forums and there are quite a few wrong descriptions of it's operation.

[POZE]

From SixShooter:
I would NEVER use a Ford inertia switch. Don't get me wrong, I like the idea, but they are overly sensitive. I've seen a bunch of Ford cars, Mustangs mostly, that when launching at the track shut off just after launch, due to the inertia switch tripping from a hard launch. A few friends that have Fords and are into wheeling have also experienced similar issues, when rock crawling or attempting steep or difficult terrain, and get a sharp jolt when tilting or maneuvering.
I'm a fan of the engine mounted oil pressure safety switch myself.

Just think how many Ford Tech's got paid an hour to reset these.
Thanks for the thoughts and warnings about the inertia switch.

[Tunedperformance]

I got that when it first came out years ago from mastercool it's a awesome tool to have

[POZE]

Just to clarify about the O-Ring fittings that are formed by my Snap-On hydraulic flare tool. I cam up with a picture from GM that shows two types of o-ring ends. The stock GM fuel line is a captured type and my Snap-On tool produces the non-captured type. The fittings don't leak but they do slightly pinch and tear the o-ring. If you notice the OD is slightly smaller where the o-ring is installed.

img021.jpg

[dyeager535]

Obviously it's just a drawing, but they show a thinner o-ring to boot. I assume you used the "stock" o-ring for that size tubing?

Has anyone found a reasonable source for the fuel proof (Viton, right?) o-rings in reasonable quantities? I visited a place in Seattle that was really knowledgable on o-rings, and had a ton of stock of them, and they made mention at the time that they sold them in a min quantity of 100. They gave me a couple free (which was all I needed) but I've not had need of a vendor since. Would be nice to get the right fuel injector o-rings, not to mention the fuel/power steering o-rings without paying GM's prices. Not that they were ridiculously expensive, but I'm sure they can be had significantly cheaper elsewhere.

[POZE]

You are correct I used the origial size of o-ring. I have not tried to find a size that is correct.

[EagleMark]

How much was a quantity of 100? Maybe we can get a few people to chip in a but a 100 each, I'd be in for 1/4 of them. I have no need for TBI injector O rings as Mr Injector gives the O rings and gaskets needed when you get your TBI or other injectors serviced.