Good morning I have a question. My 87 is not using the factory ECU to run the engine it uses an SDS standalone ECU. the only thing the factory ECU controls is the fuel pump and I think the dash display. Now for the question my car is slow to start I have to cycle the fuel pump a couple times before it will start what I want to do is put a jumper wire in the connector at the switch near the oil pressure sensor that tells the fuel pump to run full time after the oil pressure is above 4 lbs. will this work? or will it cause problems?

 

should not control dash, I don't see any parameter in the bin file aside from rev. limit start/stop which factory setting is 10000+ and 9549.
How does it control the fuel pump??
Providing there are no other mechanical/electrical issues in the fuel system,
and since you are tuning, there are a couple of ways to do this, I found the easiest is increasing the "crank pulse width multiplier vs. reference pulse" (start the numbers earlier) which allows for a faster start.
Since you didn't state if the car was somewhat modded, for a stock car this really should not be needed. In modded ones (cam etc.) this becomes common.

 

or in this case, what "slow" is...5 second crank before start is GOOD for your engine, 55 seconds is not...what does yours need ?

does your fuel pressure still hold 10 psi after 12 hours with "key off" ?...if not you will see extended "crank" time, "may" have a prob in the fuel delivery system.

your pump can be wired to run anytime it is powered, ecm needs 12v input to tell it the pump is getting power in "run" mode or MIL will be displayed.

 

I'm sorry but you must have missed the part that said I was not using the factory ecu the SDS controls the entire engine if what you said about the factory ecu not controling the dash display is true then the only thing the factory ecu is controling is the fuel pump. After the car sits for a couple days and turn the key on it takes a couple of on then off wait 5 seconds on again cycles for it to hit full fuel pressure. I would rather have the fuel pump on when the key is on. I am looking for an easy way to do this by either jumping the oil pressure switch or running a key on hot wire to the fuel pump relay but jumping the oil pressure switch sounds alot easier

 

while i cant speak for other years the 87 does indeed control the fuel pump ( more accuratly the pump relay), it turns on the pump for a 2 seconds then deactivates until the dist ref signal is detected. When the Dist ref signal is present the circuit is held energized, The oil pressure switch will simply cut power in the event of loss of oil pressure. The ECM also indirectly controls the dash as it provides the needed signals to the dash from the various monitored sensors ie vss, Oil press, Oil temp coolant temp etc.

Now to the O.P. have you measured the pressure at the fuel rail to see if full pressure is being attained during the initial 2 sec. power on cycle? and is the dist ref signal still routed to the OE ecm? according to the FSM you should have 40psi present prior to start.

if there is no ref signal routing through the ecm, then you may be better off manually controlling the pump as you have suggested, keeping the oil pressure switch in the loop for protection. Maybe even provide a 555 timer circuit configured to 2 seconds to take the place of the ECM for start up.

im sure a few other little details would have to be worked out

 

Someday maybe this myth will be stamped out. The oil pressure switch provides a parallel power source to the fuel pump when the engine has oil pressure. Losing oil pressure simply means that redundancy goes away. It DOES NOT cut power to the pump.

 

you are correct i was just looking at the FSM the oil pressure switch is only used as a backup in the event the fuel pump relay fails

In the event the relay has failed the engine must crank until 4psi is attained @ the oil pressure sensor re-energizing the fuel pump.
this will also produce the sysmptom the OP notes.

My apologies for the bad initial info.

 

The ECM powers the fuel pump relay for 2 seconds when the ignition is first turned on. The ignition must be off for 10 seconds before another 2 second priming period will be initiated by turning the ignition on again. When the engine turns over the ECM receives the pulses from the distributor and the ECM once again closed the fuel pump relay contacts running the fuel pump. Whenever the engine is turning, whether cranking or running (and the ignition is on), the ECM energizes the fuel pump relay and causes the fuel pump to be powered. As stated, when the oil pressure reaches approx 4 psi, the oil pressure switch closes and sends a redundant power supply around the fuel pump relay on a parallel circuit, directly to the fuel pump.

My guess is that the fuel pump in the OPs car is getting the 2 second priming by the ECM and that the engine is cranking to build oil pressure to close the oil pressure switch to start and run the engine. I wouldn't think with all the modifications and a separate computer, that the OE ECM is still connected to the distributor. Exactly what the OE ECM has to do with the fuel pimp would depend on what he has done with the wiring during the conversion. A hot wire from the ignition to the fuel pump or the fuel pump relay sounds like a bad idea, to me. Even though the oil pressure switch isn't a "low oil pressure engine safety shut off", at least if the engine dies, the pump will stop pumping. Not so with only ignition switch control.

The ECM ONLY controls the fuel mileage function on the digital display. It has nothing to do with gauge readouts, directly or indirectly.

RACE ON!!!

 

I agree. What you could do is use the ignition power circuit to trigger the fuel pump relay.

 

I agree. What you could do is use the ignition power circuit to trigger the fuel pump relay. Not an ideal solution, but it would work.

 

No sweat man! The rest of your explanation was spot on! I liked the thing about the timer. That would work.



Save The Wave!

 

 

 

Safety wise there is no difference whether the pump receives it's power directly from the ignition switch, or from the relay wired to the ignition switch. Either way, if the engine dies, but the ignition switch is left on, the pump will continue to run. Consider at the end of the 1/4 mile, or on a lonely road, in the middle of some really neat twisties, one dark night, where you get the car out of shape and into a ditch or a guard rail, even if the engine dies, the fuel pump will continue churning ready, willing, and able to feed a fire. Fuel for the fire, er, thought.

RACE ON!!!

 

That's why I said it's not an ideal situation.

What is would do is use a timer to run the pump long enough to get the engine started and then use the oil pressure switch to trigger the relay.
That way if the engine dies, the fuel pump stops.

 

Doesn't the SDS have a similar fuel pump control function to the stock ECU's? Most aftermarket stand-alones do.

 

Don't know anything about them but one would think so.

Perhaps the best bet is to take it to the person who installed it and get him to fix this cobbled up mess.

EDIT:Simple Digital Systems ECUs are capable of controlling the fuel pump.

 

I have blown or burned out the transistor or whatever in the ECM that sends the voltage to the fuel pump relay, on my car. I have installed a simple $5.00 push button I push to prime and for cranking. After the engine fires, it runs off of the oil pressure switch. Neat, simple, effective, and cheap.

RACE ON!!!

 

I was actually going to suggest the push button in lieu of the timer. Would work great if the wife didn't drive it!

 

the people that installed the SDS will never touch my car again they ##cked up more ##it then they fixed I will burn it to the ground before they touch it again. The sds will control the fuel pump but it will do the same thing as jumping the oil pressure switch or hot wiring the relay with a key on source and the relay kit is $180