StocRoc

iTrader: (1)

I just removed the stock ECM and harness in my 86 TPI Camaro and am going to replace it w/ the Holley Commander 950. I want to use my stock fuel pump and wire it like the picture in this post:
https://www.thirdgen.org/techbb2/sho...threadid=260766

Will this work, and if so where can I find the power wire for the fuel pump? Does anyone know off hand what color it is. Anyone forsee any problems w/ this?

thanks

Trickster

Try posting that link again, it's not coming up for me. Says it's not found.

IROCZZ3

You can do it a couple of ways...

You can wire the green/black wire from the C950 to the tan/white wire off the OEM fuel pump relay. This is direct power wire to the fuel pump, and will energize the pump if you apply 12V to it. You are bypassing the stock FP relay if you wire it this way.

Or you can do what I did and use the factory FP relay by connecting the green/black wire from the C950 to the green/white wire going to the OEM fuel pump relay. This is the wire from the stock ECM that will energize the relay for 2 seconds with key on, engine off.

StocRoc

iTrader: (1)

I'm not sure why the link isn't working, but it's in the Electronics board in the "Holley Blue Fuel Pump" thread if you want to look at it.
IROCZZ3- the thing I'm having trouble w/ is that I completely removed the stock ECM and harness, which the fuel pump relay is wired into. So with that being gone, I was going to get a standard Bosch style relay and wire it directly to the power wire from the fuel pump and energize the relay when I turn the ignition on. I just don't know where the power wire for the stock fuel pump is, or what color it is. Behind the back seat and under the carper there are 3 wires coming through the floor right where the gastank/fuel pump are. One is a ground, one is pink, and I think the other is brown or purple.l I would assume one of these would be the power wire to the fuel pump.

I'm just not sure what wire to use, or if the pump will even work correctly wired the way I have described.

Dave_Jones

I'd expect that the purple wire is your fuel level signal, and the pink wire is your fuel pump power.

One wiring setup I used to use, before converting to EFI, was to have the fuel pump relay triggered by a 5-psi oil pressure switch, and also by the purple trigger wire going to the starter. So, the fuel pump would run whenever you were cranking, or whenever the engine was running. It would also shut the engine down automatically in case oil pressure was somehow lost.

StocRoc

iTrader: (1)

Dave- thanks for the help. That's a pretty cool idea w/ the oil pressure switch. Would there be anything wrong w/ wiring the Pink Power wire to a relay and energizing the relay when the ignition is on. Will the pump shut off when it needs to, or will it just keep running? Thanks

Dave_Jones

In that case, the pump would just keep running whenever the ignition switch was in the "run" position.

The only real disadvantage I can think of, is that in the event of a crash, you're more likely to continue to pump fuel, compared to a system that automatically shuts the pump off when the engine dies. So IMHO there's at least a somewhat greater risk of fire, that could just as easily be avoided.

Also, as a minor consideration, if you have other accessories (fans, etc.) wired so that you might want to leave the key in the "run" position, with the engine off, you'd also be running your fuel pump unnecessarily.

StocRoc

iTrader: (1)

If the pump had power in the "run" position wouldn't it shut off once there was pressure in the fuel lines? What I mean is the pump can't keep pumping fuel if the engine isn't running, right? Isn't there some sort of pressure shutoff switch in the fuel pump?

That does make sense though about the crash/fire issue.

Trickster

When the key is turned to the run position, the ECM sends a two second signal to the fuel pump relay to activate the fuel pump and then shut it off until the engine starts.

StocRoc

iTrader: (1)

Right, that's what I thought. So does that mean that if I ran power directly to the fuel pump in the "run" position it would just keep pumping fuel until a line burst or something like that?

Trickster

I doubt that a line would burst but yes the pump would continue to run if you ran a hot wire to it.

StocRoc

iTrader: (1)

okay, that's basically what I needed to know. The commander 950 has a green wire that is for the fuel pump power, hopefully this turns it on and off at the correct times. Thanks for the help.

Dave_Jones

Keep in mind that in most EFI systems there is a fuel return line from the rail back to the tank. Unused fuel just keeps moving in a big circle.

There are returnless systems on some newer cars (e.g. '99-up LS1s, etc.) where the ECM modulates the pump voltage/pressure as needed, but all thirdgen-era stuff has a return line.

StocRoc

iTrader: (1)

Oh ya, I didn't even think about that. thanks guys

88tatpi

You can use almost any oil pressure/fuel pump safety switch from GM or aftermarket sources. Cost is from $7.00 to $30.00,
the tricky part is finding a place in the oil lines to tap into.

Another consideration is to change your oil sending unit(presuming you have an oil pressure guage) to the three pin type that accomodate the "oil light" and or oil pressure fuel pumps switch.
I believe the TPI Trans Am's had this three terminal oil pressure sending unit.

MrDude_1

https://www.thirdgen.org/techbb2/sho...hreadid=260766


in the future, just so you know, when people put links that have the ... in them, and they're board links, you can just take the number at the end, and stick it inplace of the number for the URL you're at.

Dave_Jones

Yup.

The GM 3-wire sender/switch is P/N 10201491. IMHO, it's the one you want, if you want a clean appearance and weathertight connectors. I've seen some T/A's with it, but also some without.

BTW, there is also a GM 2-wire switch that is externally identical in appearance, other than not having the third teminal blade. There is also at least one older GM 3-blade sender/switch, that is larger and bulkier than the P/N above. Plus, I've also seen at least 3 different styles of the 2-wire switch-only units, if you're scrounging stuff in junkyards.

88tatpi

Yes, I am aware of several versions of the oil pressure fuel pump switch. I had seen one for sale on eBay last month and the seller gave out the GM part number- it was $7.00 from the local Chevy dealer, it has the new style (TPI-TBI) plug. If I find the part # I'll put it out on the postings.
There are all sorts of these switches from aftermarket online supply stores, some websites will also have a photograph and the thread pitch and diameter of the screw-in end.
One could aslo get the fuel pump safety inertia switch for much more money ($50~$70 !!!!) that cuts-off the power to the fuel pump when the sensor is shaken enough to make it think there's been a crash. My humble opinion is to go for the simple oil pressure cut-off circuit.

Now here is where I am completely at my wit's end:

I am installing an '89TA 305 TPI motor into a 1988 C-1500 TBI Chevy truck- just a two door short bed Fleetside standard cab with TH700R4 two wheel drive Cheyenne.
The truck books mention and the old wiring harness has the oil pressure fuel pump cut-off switch.
I am using the wiring harness from an '88 Camaro Z28(350).
This harness also has the same oil pressure fuel pump cut-off switch plug. I have installed the original truck sending unit(for the guage only- one wire) into the oil line hole near the oil filter housing on the '89 TA 305 block.
Now I'm on the hunt for place to install the oil pressure F.P. switch I purchased. I cannot find it!
According to several sources there should be a hole on the back of the block near the distributor area.
I have found a hole. It was covered partially by the bellhousing of the truck's TH700R4. As the engine and tranny was installed all it took was climing over the engine with light, mirror and dremel-style electric tool with abrasive cut-off disc and in short order the tapped hole was uncovered. It seems (8mm X 1.25) more a mounting bolt hole than the much larger threaded fitting on the switch.
So I believe the tapped hole I uncovered is a mounting bolt hole and the '89TA/TPI-305 was equiped with the three prong oil sending unit incorporating the safety switch for fuel pump cut-off for low/no oil pressure.
My other alternative is to install a remote filter and oil cooler system and drill and tap a port for fitting the oil pressure switch there.
Does anyone know if; There is an oil pressure switch with a threaded end of 8X1.25mm? The bolt hole really is part of the pressurized oil circuit?

BTW:
Anyone considering to install a Pontaic/Thirdgen motor into the "older" trucks: KEEP the truck motor mounts! (truck mounts are three holers- others are four! The upper shells the parts that bolt into the block) are for the truck motor mounts ONLY!

PASSENGER CAR GM UPPER MOTORMOUNT SHELLS WILL NOT ALIGN-UP WITH LOWER TRUCK MOTOR MOUNTS.

To the untrained eye they appear to be the same- until you try to bolt everything in!!!!
I wound-up having to change motor mounts with the motor and trans in the car NOT a fun way to spend a Saturday!

Further suggestion: upon examining the prices and respective quality of the "lower" motor mounts( the rubber/steel sandwich) aftermarket(made in Mexico or India) and GM originals (uncertain-presuming USA) versus the Energy Suspension conversions(one has to drill-out the old plates and re-assemble with the trick plastic composites), I elected to call-up Summit and get the complete conversion kit (motor and trans mount).
Cost was nearly the same, a little more work but far more rewarding. I must say a call to Summit one morning and the parts arrived the next day-afternnon at no extra cost.
Sorry to say the local hot rod shops did not stock the parts and were higher priced.

Anyway, if anyone know anything about this oil switch mystery,
PLEASE enlighten this frustrated first timer small block owner!

Exhaust headers are NOT the same! Truck headers are larger diameter and bolt pattern is just slightly off even though they use the same part number exhaust gaskets!!!
To use the truck headers( AIR pump) I had to drill the header mounting holes out ever so slightly to get the exhaust bolts/studs to align correctly.

Dave_Jones

Note that in your wiring harness, it's not a cut-off switch. Rather, it's a backup to the fuel pump relay, in case of a relay failure. The ECM will keep the fuel pump energzed as long as it sees ignition pulses, whether you have oil pressure or not.

Doesn't sound like you've found the correct hole. The one you're looking for is on the TOP surface of the block (same surface as the rear side of the intake manifold seals to) and should be threaded 1/8 NPT. It's not covered by the bellhousing, and is probably within an inch or so of the back edge of the intake manifold.

88tatpi

One must remember that all fuel injected engines as most modern street and race cars with carbs too now have a recirculation line(return fuel line to the tank). With polution control laws requiring the engines to run at higher temperatures carbs were prone to perculating the fuel in the bowls and fuel lines (vapor lock!). recirculation of the fuel keeps the carb cooler and the fuel in the engine compartment. Higher fuel pressures in the fuel lines also make for a higher boiling point. Also fuel recirculation is needed in Fuel injection systems not only to purge any possible air pockets but to help in fuel pressure regulation.
Not only to prevent UNDER pressurization/delivery at the injectors but also OVER pressurization/delivery under sudden throttle lift-off. You may have notice on mechanical fuel injection systems like Hilborn(hope I'm spelling his name correctly) there is the pressure dump valve that at sudden closed throttle all that high flow/high pressure uncompressable liquid get valved back to the tank.
In some Bosch and other electronic fuel injection systems there is a fuel pressure regulator that drops fuel pressure during sudden high vacuum(throttle down) for the reason that the sudden high vacuum in the intake actually PULLS fuel out of the fuel injectors! This causes a super rich mixture, sometimes even nasty backfires , catalytic converter death and horrible polution!
It could even blow the airflow meters(the flapper valves style) completely backwards and get stuck closed. (BTW- even a small backfire in one of those older Bosch flowmeters could stick the flap shut. Most times one needs just to take off the filter housing and give it a little push.
If one leaves the fuel pump running a fuel pressure regulator will keep the fuel at the prescribed pressure and the fuel pump will continue to recirculate fuel. The advantage of an oil pressure switch is that should there be no oil pressure(engine off) the fuel pump is deactivated. This system provides a certain degree of "protection" from any situation that where having fuel running about the car is not good (dangerous!)
Any kind of crash(Heaven forbid!) that kills the engine will also cut the fuel. Of course should the oil pump fail or the oil pressure drop enough the fuel pump might cut-off in time to save the bottom end at least!

88tatpi

I will take a closer look first thing tomorrow! I did look around
near the distributor. This is an '89TA 305 TPI manifold I'm talking about. This sensor hole should be vertical, like the distributor drive?

So if all fails one can jumper the fuel pressure switch and still have some "protection" of fuel pump "over run".

Great! Thanks!

Dave_Jones

Yes, it's vertical. Just to be clear, the hole is on the block, so the type of intake manifold doesn't matter.

With a stock wiring setup, the fuel pump will run even without the switch, so no need to jumper anything. As I mentioned, the switch is only a backup device to the fuel pressure relay.

Without the relay, the car will still run, but will require several seconds of cranking, since there is no fuel until the starter motor spins enough to build 5 psi of oil pressure.

88tatpi

I found the oil port! Just where you said it was!

The situation is: the port is plugged and even the shortest sending unit/switch will not fit as the intake manifold is so ver close. I doubt a 15mm headed bolt would fit there. The plug has a square head as in standard house pipe plug.
I'm sure this '89TA 305 TPI motor had the three prong oil pressure sending unit and switch system.
Thanks again for the advise!

Dave_Jones

GM cars that use that upper oil port, ususally have some sort of adapter fitting there, vs. having the sensor screw directly into the block.

A little 1/8NPT pipe extention, and a 45° or 90° elbow, should do the trick if you don't have one of the GM fittings.

88tatpi

Oops. I guess I had vertical on the brain. Yes indeed a little 90 and the stock unit should fit....always cheaper that the three prong sending unit!

Thanks again!