Hard starting - fuel starved?

[kevinclarkwy]

Hi all - purchased a 1994 Montero 3.0L a couple months ago. *Has about 270,000 miles. So far very impressed - everything still works, air blows cold, 4wd works great, plenty of power, etc.

I am trying to resolve a problem when starting. It acts like it's starved for fuel. You have to turn the key over several times (25-30 times). *Cranking longer makes no difference. *Leaving the key on longer before attempting to start makes no difference. When it does start, it dies a few times before it will stay running. Once it's warmed up a little, it runs completely fine. I can turn it off and it will start right up again until it has sat for several hours.

This week I have replaced the fuel pump, strainer and fuel filter and it has made no difference at all. Behaves the exact same way! Hoping you all have some suggestions? Many thanks from Wyoming!

 

[Monty85]

May be test the fuel pressure ?
You could loan out the tester from parts store usually.

Or start by doing regular maintenance / tune up. Cleaning your injectors, checking compression, etc might help you diagnose more.

If unsure, I like tackling stuff by doing must do maintenances and see where it takes me.

 

[jeep-N-montero]

Hi all - purchased a 1994 Montero 3.0L a couple months ago. *Has about 270,000 miles. So far very impressed - everything still works, air blows cold, 4wd works great, plenty of power, etc.

I am trying to resolve a problem when starting. It acts like it's starved for fuel. You have to turn the key over several times (25-30 times). *Cranking longer makes no difference. *Leaving the key on longer before attempting to start makes no difference. When it does start, it dies a few times before it will stay running. Once it's warmed up a little, it runs completely fine. I can turn it off and it will start right up again until it has sat for several hours.

This week I have replaced the fuel pump, strainer and fuel filter and it has made no difference at all. Behaves the exact same way! Hoping you all have some suggestions? Many thanks from Wyoming!

Fuel pump relay good? Checked the o2 sensor and the wires going to it? Any strong fuel smell out the exhaust once it does get running?

 

[Swank Force One]

Relay wouldnt cause those symptoms. Ecu doesnt use o2 sensor for starting.

Trying to smell if it's running stupid rich is a good easy thing. FPR may be failing either open or shut.

I'd maybe want to see a leak-down test.

 

[jeep-N-montero]

Relay wouldnt cause those symptoms. Ecu doesnt use o2 sensor for starting.

Trying to smell if it's running stupid rich is a good easy thing. FPR may be failing either open or shut.

I'd maybe want to see a leak-down test.

While it may not use it for starting, if the wires are corroding or if the connection is rusting then the relay will not receive the proper signal. I speak from experience from a headache I went through with one of my Jeeps years ago, ended up being a bad ground wire on the o2 sensor that kept blowing the fuse to the ASD relay, thus not allowing the fuel pump relay to function. Worth checking anyway.

 

[Salonika]

Coolant temp sensor would be my first guess since it seems related to a temperature change. It's not throwing any codes?

 

[Swank Force One]

While it may not use it for starting, if the wires are corroding or if the connection is rusting then the relay will not receive the proper signal. I speak from experience from a headache I went through with one of my Jeeps years ago, ended up being a bad ground wire on the o2 sensor that kept blowing the fuse to the ASD relay, thus not allowing the fuel pump relay to function. Worth checking anyway.

Fuel pump relay is not on the same circuit as o2 sensor. The two never share anything, the fuel pump isn't on a PWM circuit.

I agree it's easy to check and costs nothing, but the fact that the truck does run rules out fuel pump relay.

Coolant temp sensor would be my first guess since it seems related to a temperature change. It's not throwing any codes?

This would also be something that would be ignored while cranking. Realistically all temp sensors and o2 sensors could be completely removed from the truck and it would still start.

 

[Salonika]

Pretty sure the coolant temp sensor is not ignored. The ECU needs coolant temp to decide whether cold start enrichment is required. If the engine thinks it is warm when it really isn't, the mixture could be lean enough that it won't combust. I doubt myself here a bit though because cranking 25-30 times likely wouldn't change engine temp at all.......I wonder if when he is cranking if it is a "dead crank" vs. one where you get a little combustion but not enough to fully start it. This usually can be heard as the frequency will change. A dead crank (with a strong battery) will just hold the same RPM with no change in rhythm. Fuel pressure regulator is another possibility as it uses manifold vacuum to operate?

This might be useful:
http://www.dsmtuners.com/threads/how-to-diagnose-a-no-start.217951/

 

[kevinclarkwy]

Hi all - thanks for the suggestions.

I also just tested the voltage at the electrical connection right before the fuel pump. I'm getting 10.2 volts while cranking. No power at all while the key is just on. The battery has 12.5 volts. Trying to locate the fuel pump relay now and can't find it. Been told it's under the right kick panel but so far no luck.

Once it's running no strong fuel smell, isn't running rich. And when I say it runs fine once it's warmed up, I'm talking less than a minute.

 

[Charles R]

I agree it's easy to check and costs nothing, but the fact that the truck does run rules out fuel pump relay.

I don't know anything about this Nissan, but not all fuel pumps and relays are wired the same. So this statement is not always true.

My specific example... 80's-90's GM's
The power to the pump is fed through both a relay and the oil pressure switch. A vehicle with a bad relay can still fire up and run when oil pressure is above the cut off limit. They'll just crank longer before starting sometimes.

Questions for the OP... How old is the battery? How old is the starter? Do you know if you're getting good spark while cranking?
One of the strangest causes for no starts at my work (USPS mail trucks, which are Chevy S10's under the skin) is high amp draw from the starter. The starter draw basically starves the PCM of power, and it freaks out. For these, it floods out the fuel, and we get a crazy "streaming" spark output. But the trucks cranks great! It just won't start.

I'm not saying this is your problem though. You mentioned 10.2v while cranking, and that should be fine... But if possible, confirm that voltage level at the ECM too.

Basically, you just need to start with you basics. Do you have fuel and proper fuel pressure while cranking? Do you have a proper spark at the plugs? Once you've confirmed those, THEN you move on to what sensors may be interfering with the start up by giving false info.

 

[Swank Force One]

Pretty sure the coolant temp sensor is not ignored. The ECU needs coolant temp to decide whether cold start enrichment is required. If the engine thinks it is warm when it really isn't, the mixture could be lean enough that it won't combust. I doubt myself here a bit though because cranking 25-30 times likely wouldn't change engine temp at all.......I wonder if when he is cranking if it is a "dead crank" vs. one where you get a little combustion but not enough to fully start it. This usually can be heard as the frequency will change. A dead crank (with a strong battery) will just hold the same RPM with no change in rhythm. Fuel pressure regulator is another possibility as it uses manifold vacuum to operate?

This might be useful:
http://www.dsmtuners.com/threads/how-to-diagnose-a-no-start.217951/

Yes it uses the CLT to determine if warm up enrichment is necessary, but that kicks in after it catches. I can't say for sure which way the ecu defaults to if the CLT sensor has failed, but i would bet it fails to "hey it's cold out" based on how most Japanese vehicles in the era run ridiculously rich if the CLT is bad. It would throw codes as well.

Definitely something else to check, though. But i've got $100 says that my truck will still start first time with the CLT completely unplugged.

I think pump relay is in engine bay box. Kick panel is a Sport thing.

What i'd do from here is next time you want to cold start it, jump the pump at the relay for 10-15 seconds prior to cranking it. Then see if it starts quickly.

 

[Salonika]

Well one thing to try then would be disconnecting that sensor when it wont start. I'm sure that on an otherwise operational engine, disconnecting that sensor wouldn't cause a no start, but a disconnected sensor is different to the ecu than one producing a false signal. A failed sensor is not the same as a disconnected one, sometimes they just provide bad data when they fail or are failing. If I recall that sensor is a two wire sensor, so it is probably just a resistance circuit. The ecu is probably smart enough to see zero signal and default to some type of limp mode (as can be done with a MAF), but it wouldn't know if it was being "fooled". Get a backup thermostat for your truck, and when the engine is cold, plug it into your harness then put that sensor in a cup of 200 degree water and try and start'er up. I'll bet you something would be wonky.