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No power to fuel pump


mqualey
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Hi,

I am relatively new to your site.

 

I have a 1986 Starion that won't start. Here's a little back ground; I had replaced the head with a much better after market head from Top-End Performance about a year and a half ago. I had put about 50 miles on the car and one day while it was idling to warm it up to go for a drive it just quit. I tried to start it and it turned over but would not start. It had spark so I figured it was the fuel pump I replaced the fuel pump but it still would not start. I checked the power back at the fuel pump connecter but there was no power when you turn the key on. I did some checking online and figured it was either the ECU or the fuel pump relay. I replaced the relay since that was $85 and that was cheaper than an ECU which was around a thousand dollars. Still no power back at the connector. I did not have the money to buy an ECU so the car sat for about a year until I ran across a guy that wanted to buy the car and said that he had a good ECU. We put his ECU in but it still would not start.

So I'm wondering if his ECU was really good or if there is something else causing the problem like a wire running back to the fuel pump.

 

Any ideas?

 

 

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Hidden just above the ecu is another larger relay, its tucked well up there and a pita to get at,its also powers your fuel pump,it seldom goes bad and only seen it happen once before but i believe this is the source of your problem.
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there is a fuel pump "jumper" on the front passenger side fender i can show you pictures of my 86 if you need but hot wire it first more than likely the fuel pump isnt the prob they wont come on when you turn the key on they dont energise till you turn the key to the start position i would then chk next that you have pressure to the injectors tiy can install a mech gauge were the fuel line to throttle body on the back side
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The fuel pump relay is the control relay. The fuel pump is not on when the key is on unless the car is running or cranking. What happened when the car died in the beginning may have not been the pump. Did you jumper and test the stock pump before you replaced it? Will the car run when you spray starter fluid into the throttlebody? Have you checked your spark plugs to see that they are not fouled out? Could be as simple as your injectors are dirty or leaking and the plugs fouled and the pump was fine.

 

The pump test terminal is a single wire, its a female spade terminal and originally had a cap on the end to keep it clean. Its by the cruise actuator under the hood on the passenger side. There is also an unused round connector over there too its for setting the timing only if you are at high altitude. All you do it plug a wire to that test terminal and run it over to the (+) battery terminal. That will turn the pump on its a bypass of the relay. This is nice to use if you are wanting to test fuel pressure or the pump or just to unhook the return line from the throttlebody and put a long hose on the throttlebody and put the end in a container and use the test plug so the pump can drain the fuel tank before you drop it.

 

Your ignitor may be bad. Its a black plastic box behind the coil and says "knock" on it

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I did put in new injectors about a year before this happened. They were kind of spendy so I hope they don't have to be replaced.

I did replace the fuel relay that is above the ECU so that is new.

I will hook the old pump up to the test connector under the hood and see if it works there.

I figured when you turn the key on there would be power at the pump so that's good to know that it has to be crancking.

I have to admit that I'm a little lost when it comes to computerized engines. I come from the 60's muscle car era that just had fuel and spark so they were much easier to diagnose.

I will check the things that you guys listed.

Thanks,

 

Is there a way to test the "knock" box?

 

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I did put in new injectors about a year before this happened. They were kind of spendy so I hope they don't have to be replaced.

I did replace the fuel relay that is above the ECU so that is new.

I will hook the old pump up to the test connector under the hood and see if it works there.

I figured when you turn the key on there would be power at the pump so that's good to know that it has to be crancking.

I have to admit that I'm a little lost when it comes to computerized engines. I come from the 60's muscle car era that just had fuel and spark so they were much easier to diagnose.

I will check the things that you guys listed.

Thanks,

 

Is there a way to test the "knock" box?

If there is spark its not the knock box (ignitor).

 

Put 12v+ to the test terminal to see if your current pump is working.

 

Did you replace the injector clips?

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If you pull the coil wire from the cap and lay it near the negative battery do you have a spark when you crank the motor over? When the plastic ignitor boxes start to die they do strange things there isn't a way to test them to know they may work today and not tomorrow and half work the day after. Best thing to do is wire in from from an 88/89 that is in a metal box those are much more reliable. Injectors can be cleaned so if you have to old ones you might do that for a spare set. The test port for the pump you'll still have to plug the pump in back at the tank but if you have the pump out just put some jumper wires on it and hook it to a battery and see if it runs.
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If there is spark its not the knock box (ignitor).

 

Put 12v+ to the test terminal to see if your current pump is working.

 

Did you replace the injector clips?

I did not replace the injector clips. Do parts stores have those or are they a special order item?

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If you pull the coil wire from the cap and lay it near the negative battery do you have a spark when you crank the motor over? When the plastic ignitor boxes start to die they do strange things there isn't a way to test them to know they may work today and not tomorrow and half work the day after. Best thing to do is wire in from from an 88/89 that is in a metal box those are much more reliable. Injectors can be cleaned so if you have to old ones you might do that for a spare set. The test port for the pump you'll still have to plug the pump in back at the tank but if you have the pump out just put some jumper wires on it and hook it to a battery and see if it runs.

I will hook the pump up to the battery to see if it runs. Is it possible for the pump to run but not put out enough pressure? I read some where that some injectors won't spray if they don't have enough pressure.

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For a StarQuest to start, it needs fuel and ignition in the proper amounts and at the proper time.

The ECU won't command fuel though until it sees/verifies spark is present so start there.

 

With the ignition key ON or in START you should have +12volts on the ignition coil "+" post. If not, the IGN fusible link or the ignition switch is kaputt.

 

Then, do the test Indiana suggested - crank the engine with the high-tension ignition wire disconnected from the distributor and instead near a good ground bolt. I use the suspension mounting nuts... While the engine is cranking, you should be able to see and hear a solid spark. If not, the ignition system is not working. Usually if the ignition is dead the dash tachometer will read nothing; if the ignition is trying the tach will wiggle/bounce a little.

 

Once you have verified spark, the next step is to very fuel. One simple thing to try: swap the electrical connectors on the two fuel injectors. If that makes the engine start, the "primary" (black plastic) injector is bad. If that doesn't help, undo the electrical clips. Turn the ignition key ON and leave it... measure the voltage from ground to one wire of the primary injector clip. One of the two wires should read +12volts. If you can't get the voltage, the ECI fusible link, ECI relay, or the injector ballast resistor (bolted to bodywork between air filter and headlight, gotta remove the air filter box to get to it) is shot.

 

If you find +12volts on each injector, all that's left is the ECU, the sensors that feed the ECU, or a fuel pump/fuel line issue. The main signal for starting/cranking is the airflow sensor. The white+black wire is the output... put the voltmeter (set to read DC volts) on that wire. With the key ON you should see almost no voltage... try cranking. The voltage should climb a bit to roughly 1 to 2 volts. If not, the airflow sensor is bad or there is a massive air leak in the air lines.

 

The ECU grounds the "other" wire (the non-12volt wire) of an injector to fire that injector; it grounds the wire in sync with airflow sensor pulses. Bad wiring, or corroded/rotted connectors at the ECU terminals (windshield leaks drain water down the bodywork "A" pillar right onto the ECU...) can cause the problem.

 

Of course the whole fuel injection process relies on at least 36psi pressure at the injectors. A dying pump, crushed fuel pipes under the car, or clogged fuel pick-up socks/filters will restrict fuel flow. The in-take pick-up commonly gets filthy as does the dinky "cone" filter on the fuel pump inlet. You can access both via the access hatch in the trunk floor - pop the hatch; lift the false floor, and remove the single screw on the black metal plate you'll see on the driver side of the floor. Pry that plate free (sealant goop...) and you'll see a round piece bolted to the fuel tank and the hoses from that to the fuel pump. Undo the fat hose to the pump; the cone filter will be in the pump-end of this hose or in the pump itself. Clean it. Then knock the dirt/crud off the round piece and undo each screw about 1 turn each, go to the next screw and loosen it one turn, etc... round-n-round doing each screw a turn at a time to evenly loosen this plate. Lift the plate straight up; the fuel pick-up "reaches" towards the center of the tank so it'll take some wiggling to get it in/out. Clean the filter at the end of this assembly. During re-assembly, the pick-up filter sits in some baffles in the tank so you have to pay attention to get these parts lined up.

 

The only real way to test fuel pressure is to hook a mechanical fuel pressure gauge (or an electric one if you want to spend time the time wiring it) to the top/rear of the injection mixer (throttle body) assembly... there's a hex plug that'll unscrew in the top part of the mixer assembly. You should see +36psi while cranking the engine.

 

mike c.

 

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The fuel pump gets power via the ECI fusible link, the ECI relay, and a ground. The ECI relay is turned ON by the ignition key START position to get the car started; the ECU holds the relay ON once the ECU "sees" pulses from the ignition module. There is a one-wire test connector hanging from, or taped to, the wire harness bundle between the air filter canister and the fender. It'll be black+white wire with a protective cap on the connector. That wire is the same wire as the one from the ECI relay to the fuel pump - i.e. it should have +12volts during cranking.

 

You can also jumper this connector to the battery "+" post to make the pump run for testing. You'll hear a whirring sound as fuel flows through the injection mixer assembly if the pump is trying to work though that won't tell you if you have enough fuel pressure or not.

 

mike c.

 

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