Slant Six Forum :: EFI Slant

Quote:

thanks! so they just milled the rail for two sizes and the ring is what holds it right?(beside the obvious mounts on the rail)

The fuel rail was milled for the injectors, however there is only one size. Yes, the o-ring is what keeps the rail and injector in place. Dash-6 fittings were welded to each end of the rail to accept the fuel inlet and return lines.

This is basically what I started with: eBay Dash-6 fuel rail

Why not add a "start" relay, to the fuel pump circuit?

I see the logic in that. I wonder if I can use my factory oil-pressure switch to trigger the relay?

I need to build fuel pressure before I start the motor - i.e. ignition on, let the fuel pumps pump for 5-10seconds

When you first turn on the system there's no charge on the capacitor. While the capacitor is getting charged it acts like a normal ground until it gets charged up. Once charged, the fuel pump relay shuts off. I got the capacitor for about a buck at an industrial liquidator and it's capacity is around 30,000 mfd. You may need to experiment on size to get the fuel pump run time you want.

Thanks. I will install a check valve in my fuel system. I guess that would cure the slow start after it has set a few days. Is there a part number out there anyone can recommend?
Sam

Author:	slanting78 [ Mon Apr 09, 2007 6:28 pm ]
Post subject:
Quote: Quote: thanks! so they just milled the rail for two sizes and the ring is what holds it right?(beside the obvious mounts on the rail) The fuel rail was milled for the injectors, however there is only one size. Yes, the o-ring is what keeps the rail and injector in place. Dash-6 fittings were welded to each end of the rail to accept the fuel inlet and return lines. This is basically what I started with: eBay Dash-6 fuel rail thanks for being patient, i am highly interested in doing efi like everyones on my own slant and other cars.

Author:	VE Safari [ Fri Apr 27, 2007 8:11 pm ]
Post subject:	EFI startup issue resolved
A quick update - my cold start problem has been resolved. Pretty stupid in hindsight, but the fuel pump relay was wired to a "run" circuit, not a "start" circuit. Turn the reds on and the fuel pumps whir away and do their thing, turn the key to start and the pumps stop - problem was you could not hear them stop because of the starter noise. Change the relay trigger and the car will start without the test-mode process described in an earlier post. So why only this problem when the car was cold? I'm guessing because I don't have fuel pressure check valve, which maintains line pressure when the engine is off. Slowly overtime the pressure drops in the fuel line, so when I'm cranking there is no fuel in the system to inject. When the car has been run for a while pressure exists and has not diminished or drained back, so when I go to restart the injectors have fuel despite the pumps not working. Certainly enough fuel for the car to fire, at which time the pumps come back on and everything works as it should. That's my theory anyway! I've ordered a check valve, so hopefully everything will be resolved within the next couple of weeks.

Author:	Charrlie_S [ Sat Apr 28, 2007 4:17 am ]
Post subject:
Why not add a "start" relay, to the fuel pump circuit?

Author:	VE Safari [ Sat Apr 28, 2007 8:14 am ]
Post subject:
Quote: Why not add a "start" relay, to the fuel pump circuit? I'm not sure if I understand what you are suggesting here? Add another relay? I ended up moving the fuel pump relay trigger from my fuse-box to the ECU. Basically if the ECU has power, my fuel pumps have power. Seems to work fine so far.

Author:	dakight [ Sat Apr 28, 2007 8:26 am ]
Post subject:
The only problem with that is in case of accident it will continue to pump fuel even though the engine is not running. If there's a broken fuel line and/or a fire that would potentially be a very serious situation. With the oil pressure switch controlling power and a seperate relay to provide power until the engine lights off and builds oil pressure that situation is prevented.

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Author:	VE Safari [ Sat Apr 28, 2007 9:48 am ]
Post subject:
I see the logic in that. I wonder if I can use my factory oil-pressure switch to trigger the relay? Problem there is I need to build fuel pressure before I start the motor - i.e. ignition on, let the fuel pumps pump for 5-10seconds, start. That wouldn't work if I wire up the fuel relay to the oil pressure switch... Anyway, it's 2.45am and I need so shut-eye. I'll have a think about this in the morning when I'm fresh. In the meantime please feel free to suggest how you would wire this thing. cheers, Eyman

Author:	SlantSixDan [ Sat Apr 28, 2007 10:33 am ]
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Quote: I see the logic in that. I wonder if I can use my factory oil-pressure switch to trigger the relay? Yes, you can, as long as you've got an oil pressure sender that's equipped to run an oil pressure warning light, and not just to run a gauge. There is a combo sender available if you're running a gauge and a light. Beyond that, all you need is a normally-closed relay with its terminal #85 tapped into the oil pressure warning light wire. Terminal #86 gets key-switched +12v. Terminal #30 via a fuse to key-switched +12v. Terminal #87a to the fuel pump relay's terminal #86. Then you run a wire from the small (solenoid) terminal on your starter motor to terminal #86 of the fuel pump relay. The result of this setup: When the oil light is illuminated (no oil pressure), the relay will be open, and the fuel pump relay will not activate. When the starter motor is operating, power will be shunted to the fuel pump relay to run the fuel pump during cranking regardless of oil pressure. If the engine stalls or oil pressure is lost, the fuel pump relay will be deactivated and the fuel pump will stop. Quote: I need to build fuel pressure before I start the motor - i.e. ignition on, let the fuel pumps pump for 5-10seconds Wow, that long...? Why? I would think a quick 1-second fuel pump burst would be more than adequate to build pressure, in which case the starter solenoid fuel pump actuation described above would be adequte. But if for whatever reason you really need 5-10 seconds' worth of priming, there are a couple ways you can do this. You could install a manual primer button on the dashboard consisting of a momentary-contact pushbutton switch fed by +12v and feeding terminal #86 of the fuel pump relay. As long as you hold the primer button, the fuel pump runs. That'd be the simplest way to do it. If you want to automate the process, you could install a timer relay with 5- or 10-second release delay and hook it into the dome light switch on the driver's door such that when the door is opened, it'd trigger the timer relay, which would run the fuel pump for your 5 or 10 seconds. By the time you'd got your seatbelt on and the key in the ignition, the system would be all primed and ready to start. But I'm still curious why such a long priming period should be needed...

Author:	emsvitil [ Sat Apr 28, 2007 12:11 pm ]
Post subject:	Cheap timer.......
My truck had a problem with fuel pressure after sitting awhile. It didn't have a circuit to prime the pressure, so after sitting the pressure would eventually be lost and it took some cranking to bring it back up...... Anyway, it did have a test connector for testing the fuel pump without running the engine. The test connector was an additional ground path for the fuel pump relay. (if you don't have the test connector, run a wire for this additional ground to the 'cheap timer') Anyway, the 'cheap timer' is to get a large capacitor and hook it up the extra ground wire. When you first turn on the system there's no charge on the capacitor. While the capacitor is getting charged it acts like a normal ground until it gets charged up. Once charged, the fuel pump relay shuts off. I got the capacitor for about a buck at an industrial liquidator and it's capacity is around 30,000 mfd........ You may need to experiment on size to get the fuel pump run time you want.

Author:	SlantSixDan [ Sat Apr 28, 2007 3:11 pm ]
Post subject:	Re: Cheap timer.......
Quote: When you first turn on the system there's no charge on the capacitor. While the capacitor is getting charged it acts like a normal ground until it gets charged up. Once charged, the fuel pump relay shuts off. I got the capacitor for about a buck at an industrial liquidator and it's capacity is around 30,000 mfd. You may need to experiment on size to get the fuel pump run time you want. This elegant solution makes me smile.

Author:	VE Safari [ Sun Apr 29, 2007 7:04 am ]
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Thanks for the suggestions, there certainly is a lot of knowledge around. I now think I've got it right, as per the ECU manufacturer's wiring diagram. Apologies in advance if my terminology is not correct. The ECU switches the fuel pumps on and off. The fuel pump relay has two inputs from the ECU. Trigger (terminal 86) and gnd (terminal 85). I changed my +ve trigger source from a post on the fuse box to the "ignition on" wire from the ecu, as per the MicroTech wiring diagram. Terminal 85 is an earth trigger from the ECU. Basically when the engine shows zero rpm, 85 open circuits and the relay shuts off thereby cutting power to the pumps. So whenever the engine stops firing (like in a crash-type situation, or if the engine stalls) the fuel pumps shut off. What the ECU also does is if you leave the ignition on for 15seconds or longer without starting the motor, it shuts the pumps off. I have been using this feature to prime my fuel system. Why do I need to prime my fuel system for so long? I believe I do have a fuel delivery problem. My lift pump is suspect, and I think that it takes a while to fill my surge tank. I believe I get drain-back once the car is parked, and after a long park (say 4-5 hours) she fails to start, which brings us back to the start procedure which prefaced all this discussion. I got both fuel pumps from a wrecking yard out of 20 year old GM cars. It turns out I don't need to prime the system for quite so long, but 3-5 seconds is definately required when the motor is left overnight. If she has been driven and parked (like going to the shops and returning), no priming is required - I can lean in the window and turn the key and she will start first click. I'm hoping that a one-way valve placed on the fuel line will prevent drain back through the pumps and hold pressure in the fuel rail overnight, enough to start the car without priming.

Author:	Sam Powell [ Sun Apr 29, 2007 1:25 pm ]
Post subject:
Does anyone have a part number for a fuel line check valve? If you have a through system that inputs at one end of the rail, and then goes to the pressure regulator, will a check valve bfore the rail do its job of maintaing pressure in the rail. What keeps the fuel from simply flowing on through the regulator, and pressure being lost? Sam

Author:	SlantSixDan [ Sun Apr 29, 2007 2:07 pm ]
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The check valve's job is to prevent fuel draining back via the supply side of the system, down through the lines and backwards through the fuel pump into the tank. The fuel pressure regulator is the return-side check valve! If it's open and letting fuel flow when the engine's not running, it's bad and needs replacement.

Author:	Sam Powell [ Sun Apr 29, 2007 3:03 pm ]
Post subject:
Thanks. I will install a check valve in my fuel system. I guess that would cure the slow start after it has set a few days. Is there a part number out there anyone can recommend? Sam

Author:	VE Safari [ Sun Apr 29, 2007 6:54 pm ]
Post subject:
Quote: Thanks. I will install a check valve in my fuel system. I guess that would cure the slow start after it has set a few days. Is there a part number out there anyone can recommend? Sam Here is a nice Aeromotive one: Summit Racing

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Author:	VE Safari [ Mon Apr 30, 2007 6:53 am ]
Post subject:
Here is the check valve I bought today for $35, along with the two -6 barb fittings for $6/each. I finally got the idle control valve fitted to a suitable mounting plate. Now to find some where to fit it. I'm leaning towards the accelerator cable bracket at this point. I've got a little free hoist time booked at my friend's workshop tomorrow night, so hopefully I can get everything fitted up.