Intermittent Cranking No Start, Pump Gas Peddle To Start (1 Viewer)

[landtoy80]

Recently I have had an intermittent starting problem. I crank the motor but it just cranks. I turn off key and then as I crank the motor, I pump the gas peddle and it will start and run rough for a few minutes.

I have had a similar starting issue but it was when I "short started the motor" as I call it. That is, I crank to the point that it normally starts but stop cranking before motor starts, I then have to pump the accelerator peddle to get it to start just like its doing now.

Not sure what is happening when you have to pump the gas peddle to get it to start? Could it be not getting fuel or flooding or other issue?

Most of the time after about 3 sometimes 4 pops of the motor (sounds like a cylinder compresses then valves open like when you are testing compression) the motor normally starts.

New plugs, fuel pump has about 150,000 +/- on it, fuel filter maybe the same miles as fuel pump. 95,000 mi on O2's but get intermittent 25 and or 26 CEL but I get both intermittent for years.

 

[MDarius]

At the risk of stating the obvious, have you gone through the standard tune up items? Distributor, wires, plugs, checked pressure at the fuel rail, on to injectors...Spark, fuel, and air, right? 150k is a lot for a fuel filter IMO.

 

[landtoy80]

Cap/rotor is new last summer, cleaned the carbon off week ago. New plugs. Checked timing.

I can unplug the O2's and see that helps. Drove a year or so with them unplugged with no issues.

Have not checked fuel rail pressure, don't have a gauge. Guess I could remove fuel line and see if gas is flowing.

It's hard to diagnose as it happens when I need to go somewhere. Would be nice, when it happens, i could check for spark. But pumping the gas should not affect spark???

 

[MDarius]

... Guess I could remove fuel line and see if gas is flowing.

It sounds like a fuel delivery problem to me. Of course, I'm usually the guy asking the questions, not answering them. So, take it for what it's worth. Nobody else was chiming in and I took pity on you to venture a guess. I would start looking at fuel pump threads. My recollection is that the easiest place to test flow is at the rail. If that's good I'd go to injectors.

My brother-in-law was a great mechanic. The one rule he taught me was that when you are troubleshooting, start with easy and cheap and work up to hard and expensive.

TPS COULD be a culprit. Sorry I'm not the IH8MUD hero you need in this one.

 

[ZackR]

Does it happen all of the time or only after very short start stop cycles (aka lawnmower syndrome)? The only times I've had to use the gas pedal to start a fuel injected engine was after moving the car a few feet in the driveway a few times, resulting in fuel wash that killed compression. I haven't had this issue on the cruiser but it could happen.

 

[landtoy80]

Its fine on warm or hot or short trips startups. Its after motor is cold/siting over night.

Does the motor have to crank a certain number of cranks or does oil pressure have to build up before spark or fuel injectors turn on?
I have always though that the motor turns over a certain amount before it starts OR oil pressure has to build up before ECU will let the motor start BUT I am just assuming this.

 

[ZackR]

I'm almost positive the oil pressure signal doesn't affect the ECU signal for engine cranking or starting. About a month ago my gauges were all offline due to a blown fuse (including oil pressure) and there was no difference in starting or running. I had to drive it like this a few times with all gauges at rest before it was repaired, so there were multiple start/stop cycles.

As for revolutions before spark I don't know the answer. I would assume the engine would spark/start as soon as it possibly could.

 

[ajax1]

Usually if it sits overnight or long time and doesn't start you have a injector leaking down losing pressure so you could have bad injector,

 

[landtoy80]

Reading in the FSM I found cranking that injectors don't inject fuel for less than 3 seconds.

ON-VEHICLE INSPECTION SPARK TEST

CHECK THAT SPARK OCCURS

(a) Disconnect the high-tension cords (from the ignition coil) from the distributor cap.

(b) Hold the end approx. 12.5 mm (0.50 in.) from the body ground.

(c) Check if spark occurs while engine is being cranked. HINT: To prevent gasoline from being injected from
injectors during this test, crank the engine for no more than 1 - 2 seconds at a time.



This enplanes why motor doesn't start for a couple seconds

Wonder if something is causing my injectors not to inject fuel into the cylinder?

If motor were flooded, would pumping the peddle work to start motor?

 

[GeoRoss]

Could the fuel rail be loosening pressure overnight?

 

[Reelitchy]

Sounds like maybe your iac is not open, could also be the ecu coolant temp sensor