Fuel Pump Relay Question?

88 S-10 Blazer 4.3 4x4 AT.I finally put a ecm in and now sometimes it fails to start.If I bypass the fuel pump relay it fires right up,I also have a new oil sending unit.The manuals I have says if its running and
engine at normal operating temp.it is supposed to keep running with the fuel pump relay disconnected,which it doesn't.Engine dies when disconected.My question is could I have an open wire to the oil sender?The fuel relay socket is real loose and needs replaced.Could this be the problem?Thanks for any input on this. Bobby
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I put another fuel pump relay pigtail on it today.Some times it cranks alot before it fires up.It also stored a code 54.If someone here could lead me in the right direction,I sure would appreciate it.Thanks for any suggestions. Bobby
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I connected an ignition wire to the fuel pump prime connector,and the engine runs good.I would like to get the 2 second signal back to the relay.I checked the ground wire (black-white}on the left back side of engine,that was ok.Can anyone here tell me what else I can check?Thanks! Bobby
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Can you tell me where I can locate the problem,to my previous question on why my 2 sec. ecm signal isn't getting to my relay?Thanks! Bobby
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bobby swift wrote:

==================== Do this.......... and post the results... ! ! ! !
Unplug the Relay.
Unplug the fuelpump oil pres. sensor.
Take your jumper wire off of the prime connector.
Check for power on the tan/white wire at the prime connector when the ign. key is turned to the on position. You should get voltage for 2 seconds.
then.........
Check for power at the orange wire on the relay, and the orange wire at the fuel pump oil pres. sensor.
Hook everything back up and drive the truck untill you do the repost. ! ! .
FACTS........ the orange wire is battery feed for the oil pres. sensor AND the relay.
the tan/white wire at the prime connector is the 2 second feed line from the ECM.
the ECM has an internal driver that is timed. The only thing feeding the 2 second prime circuit on initial ignition run IS the ECM. No other inputs are telling the ECM to turn on the prime circuit, IT IS a programed logic of the ECM.
the tan/white wire is tied into the OUTPUT circuits of the relay and the fuel pump oil pres. sensor.
the tan/white wire from the oil pres. sens. has power ONLY after the eng. oil pres. reaches at least 4-5psi.
the tan/white wire from the relay has power ONLY after the ECM detects a rpm signal from the crank sensor.
the orange wire at the relay and at the oil pres sensor are the same wire (spliced)
the orange wire must have power with key on.
the orange wire must have power with key on/eng running.
THE ORANGE WIRE FEEDS THE WHITE/TAN WIRE after the relay or the oil pres sensor switches on.
the tan/white wire ONLY HAS POWER when the ECM initially energizes the circuit for 2 seconds, or after the relay OR the oil pres. sensor are switched on. The ECM no longer feeds the wire after the initial 2 second signal.
these wires are spliced in several locations, and have an aproximate overall combined length of at least 10-15 feet. So that's what your working with.
LAST TWO FACTS.......
Your working with a bunch of wire hooked into 4 switches. A simple circuit.
I'm gonna git pissed and call you names on usenet if you don't check those 2 wires I told you to check and do a repost by Sunday afternoon.
~:~ Marsh Monster ~sips his crownroyal....takes a hit off his dooby.......wonders if you would like to just ADD a new 2 second signal generator to the line and forget about the ecm altogeather...... <g>~
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I'm getting power to the fuel pump relay(orange wire)with switch on and off. No other signal on fuel pump relay.Just the signal on gray wire with engine running,gets signal when cranking about ten times or more,then fires and runs fine. There are 3 wires on oil pressure sensor (2 orange-black -1 tan)no current with switch on or off.I am pretty sure there is a signal when cranking and run,I will check and let you know later.When I first installed the other ECC it was getting the signal off and on for a while.I thought it was fixed,but not.It does store a code 54 every now and then,but doesn't when running in bypass through the prime connector(gray wire).The fuel pump relay wires are(black-white stripe--Gray---Orange---Pink -black.Thanks Marsh for the info.I'll keep you up to date! Bobby
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I just whent out and checked the prime connector for current with ign. on there is none,it only has current when it cranks,and it starts and runs after a lot of cranking.Maybe the computer lost ground somewhere?Or went kapoo!It worked great when I first put the computer in.I drove it to the Mall,cut it off and it wouldn't run till I bypassed the relay.I'' keep trying to figure this out.Thanks Again Marsh! Bobby
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bobby swift wrote:

==================== How long after you put in the ECM did the symptom stay away?
any whooo.... I'll gander at the schematic some more and compare what you've posted.
~:~ marsh ~:~
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