Erratic Starting Problem

[freedom5]

My 87 Ranger has recently had an erratic starting problem. It sometimes takes a couple of tries before it starts. Once it starts it runs smooth, accelerates good and shows no other problems. I am guessing it may be the fuel pressure regulator leaking back and not keeping fuel available until the electric pump builds the pressure. Any thoughts will be appreciated.

There is no signs of any external leaks of smell of gasoline.

 

[RonD]

Probably not fuel pressure regulator(FPR), hard for that to be intermittent.
Unless you failed to mention that it is only hard to start after sitting longer.
i.e. if it sits for 2 hours it starts right up, if it sits for 8 hours it is hard to start
Then yes, could be losing fuel pressure via FPR or check valve in fuel pump.

You have 2 fuel pumps on an '87, one in the tank(low pressure) and one in the frame rail under drivers seat(high pressure).

Fuel pumps are electric motors and electric motors can be intermittent when starting up, once they are turning/running they will generally stay running, which fits your symptoms.

Each time time you turn on the key both pumps should run for 2 seconds and then shut off, it is a safety feature so pumps won't keep running if engine stalls(0 RPMs) as in an accident or roll over.

But that 2 seconds should be long enough to feel/hear a pump running, have someone cycle key on and off while you are under truck.

Also cycle key on and off a few times before trying to start engine, if you are losing fuel pressure running the pumps a few times will build it back up.

 

[freedom5]

Thanks - I'll check it out.

 

[freedom5]

Probably not fuel pressure regulator(FPR), hard for that to be intermittent.
Unless you failed to mention that it is only hard to start after sitting longer.
i.e. if it sits for 2 hours it starts right up, if it sits for 8 hours it is hard to start
Then yes, could be losing fuel pressure via FPR or check valve in fuel pump.

You have 2 fuel pumps on an '87, one in the tank(low pressure) and one in the frame rail under drivers seat(high pressure).

Fuel pumps are electric motors and electric motors can be intermittent when starting up, once they are turning/running they will generally stay running, which fits your symptoms.

Each time time you turn on the key both pumps should run for 2 seconds and then shut off, it is a safety feature so pumps won't keep running if engine stalls(0 RPMs) as in an accident or roll over.

But that 2 seconds should be long enough to feel/hear a pump running, have someone cycle key on and off while you are under truck.

Also cycle key on and off a few times before trying to start engine, if you are losing fuel pressure running the pumps a few times will build it back up.

It starts right up after sitting for awhile. it has two cooling sensors the engine coolant sensor and the air charge temperature sensor. I changed both sensors several years ago. I'm wondering if it could be the air charge sensor which connects to the engine control module and the throttle position sensor.

 

[RonD]

If you count the IAT(intake air temp) sensor then that are actually 3 temp devices.

IAT sensor
ECT(engine coolant temp) sensor, used by computer to set Choke Mode, and Closed loop
ECT sender, only used by dash board gauge

Sender only has 1 wire, sensors 2 wires

But you are right only 2 sensors, but 1 sender

No, probably not IAT sensor, it plays a very minor roll in fine tuning air/fuel mix.
ECT sensor is very important, especially for cold starts, cold engine needs more fuel and higher idle to stay running, what the choke plate did on a carb.
With Fuel Injection the computer must do this, which is why the ECT sensor exists.

If ECT sensor was the problem then engine could be hard to start, but only cold, and would have a low cold idle, should be 1,000+ RPMs cold.

Also what engine do you have?

 

[freedom5]

If you count the IAT(intake air temp) sensor then that are actually 3 temp devices.

IAT sensor
ECT(engine coolant temp) sensor, used by computer to set Choke Mode, and Closed loop
ECT sender, only used by dash board gauge

Sender only has 1 wire, sensors 2 wires

But you are right only 2 sensors, but 1 sender

No, probably not IAT sensor, it plays a very minor roll in fine tuning air/fuel mix.
ECT sensor is very important, especially for cold starts, cold engine needs more fuel and higher idle to stay running, what the choke plate did on a carb.
With Fuel Injection the computer must do this, which is why the ECT sensor exists.

If ECT sensor was the problem then engine could be hard to start, but only cold, and would have a low cold idle, should be 1,000+ RPMs cold.

Also what engine do you have?

My engine is a 2.9