3FE cold start woes

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Feb 16, 2019
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61
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Location
Raleigh, NC
Hey all, on these brisk NC spring mornings, my FJ62 has had a lot of trouble cranking over. Occasionally when it does turn over, the CEL will come on and any depression on the accelerator pedal will drop RPMs and choke out the engine.

I had the local shop check and replace vacuum lines that needed it and they couldn’t get the problem to reproduce. It also doesn’t seem to happen again once the truck has started for the day or if it’s a warm morning.

Any ideas or threads I should check out?
 
You mean the starter turns slowly or the trunk cranks a long time before the engine starts?
 
Clean the cold start injector.

How old are the spark plugs?
 
Photo below, circled is the cold start injector on the 3FE. It’s on the driver side of intake just above the EGR assembly (which happens to be removed in this photo)

757CCDC4-48CF-4931-BBBB-86E7B5B321E5.jpeg
 
I'll give that a cleaning today. I'm not sure how old the spark plugs are, but I haven't had them serviced in the year and a half I've owned the truck.
 
Gents, I'm having the same type of issues. I have a 90 FJ62. I recently replaced a bad starter. Since replacing the starter, the engine seems to have a hard time cranking over. Not sure if this is a starter issue or something else. The starter was new from Cruiser Corp. Any ideas?
 
Gents, I'm having the same type of issues. I have a 90 FJ62. I recently replaced a bad starter. Since replacing the starter, the engine seems to have a hard time cranking over. Not sure if this is a starter issue or something else. The starter was new from Cruiser Corp. Any ideas?
Go through the same process we mentioned on this thread.
Check your spark plugs,wires, then go to your cold start switch and clean it up.
 
Fuel injection has a few basic things:

1. A computer (ECU) that is really just a storage space for a whole bunch of tables of information (think excel spreadsheets). The ECU pulls information from a bunch of sensors, cross references that info through its database, and then outputs a set of commands to the fuel injectors telling them to spray more or less fuel.

2. Sensors
- a, coolant temp
- b, crank shaft position
- c, air flow, air mass, or manifold pressure
- d, Oxygen sensor


those are the basics. When the engine is cold it relies on the coolant temp sensor, whichever timing sensor its using, and the air sensor of choice to start the engine and run the engine. Some system use a cold start injector to help spray additional fuel into the engine to aid in startup.

The EFI system is smart and quite good at reacting to system adversity but if timing is way off, or vacuum leaks are excessive, grounds are bad, or battery voltage is low then you will have problems. Cold start problems in EFI vehicles where things are sealed properly and mechanically healthy often point to a bad or sluggish cooltant temp sensor or sometimes dirt air mass/flow sensors.

But like any problem always start with the easy stuff and then start proving which systems are not the cause. Grounds, battery terminals and cables, air leaks, fuel leaks, spark plug gap and health, ignition components, filters, fuel quality and pressure, valve adjustment etc etc.
 
Fuel injection has a few basic things:

1. A computer (ECU) that is really just a storage space for a whole bunch of tables of information (think excel spreadsheets). The ECU pulls information from a bunch of sensors, cross references that info through its database, and then outputs a set of commands to the fuel injectors telling them to spray more or less fuel.

2. Sensors
- a, coolant temp
- b, crank shaft position
- c, air flow, air mass, or manifold pressure
- d, Oxygen sensor


those are the basics. When the engine is cold it relies on the coolant temp sensor, whichever timing sensor its using, and the air sensor of choice to start the engine and run the engine. Some system use a cold start injector to help spray additional fuel into the engine to aid in startup.

The EFI system is smart and quite good at reacting to system adversity but if timing is way off, or vacuum leaks are excessive, grounds are bad, or battery voltage is low then you will have problems. Cold start problems in EFI vehicles where things are sealed properly and mechanically healthy often point to a bad or sluggish cooltant temp sensor or sometimes dirt air mass/flow sensors.

But like any problem always start with the easy stuff and then start proving which systems are not the cause. Grounds, battery terminals and cables, air leaks, fuel leaks, spark plug gap and health, ignition components, filters, fuel quality and pressure, valve adjustment etc etc.
This should probably be stickied for people who are having trouble getting an engine to run. Going over this eliminates a lot of issues people seem to have
 
Ok. Thanks.

What portion of the cold start switch do you remove? Do you remove the cold start switch directly from the manifold or where the gas line is? Or both? I have no gasket seal to seal it up if required. I'll have to brave the infectious world outside to to get some if needed.
 
I'll bet my temp sender is bad too, my temp gauge never rises from the 0 position.

The gage temp sensor is different than the one that the EFI uses. Also the gage sensor is often fine and its common that the wire which connects to the gage is broken.
 
Sensor that drives the gage is not an input to the ECU. There is a dedicated sensor for that.

To add to Seth's list is the Throttle Position Sensor on the 3FE. If not adjusted correctly or is malfunctioning it can cause all kinds of issues. Also the Air Flow Meter (not mass air flow on this engine) has a switch that controls the fuel pump relay. Can cause issues as well.
 
Sensor that drives the gage is not an input to the ECU. There is a dedicated sensor for that.

To add to Seth's list is the Throttle Position Sensor on the 3FE. If not adjusted correctly or is malfunctioning it can cause all kinds of issues. Also the Air Flow Meter (not mass air flow on this engine) has a switch that controls the fuel pump relay. Can cause issues as well.


Good call....I knew I was missing something from the list.
 

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