Car will only start with starting fluid, then runs fine once going

Does it fail to start like this even when the engine is fully warmed up?

If so, the rail fuel pressure test is the place to start.

If it starts ok with a fully warm engine, and fails to start when cold, then I’d tend to suspect something wrong with the cold-start enrichment function. How this works varies from car to car, but one way or another extra gas will be injected on cold starts. The problem would most likely be either that the cold start condition isn’t being detected (some kind of sensor problem) or something is preventing the extra gas from being injected (ECM or injector problem or fuel pressure problem).

It does the same thing warm or cold on this one. Even if you shut it off and go back at it you need a shot of starting fluid to get it going then it’s fine to leave on.

The coolant temp sensor would be a viable culprit then? I just replaced my crankshaft position sensor which remedied my stall, no crank, no start (when warm). It works great now (besides not starting at all now). I see people posting about putting the car in “learn mode” after changing the cks. I don’t have experience with that.

Since your engine fails to start hot or cold, the fuel pressure is where to start. If you are waiting on the fuel pressure gauge adapter, testing the coolant temp sensor is worth a try. I don’t think you’d even have to remove the sensor. All you’d have to do is measure the resistance when the car has sat overnight, then compare the measurement to what it should be at that temperature. Make sure you are testing the correct coolant temp sensor. Many cars have two, one is only used for the dashboard gauge. It’s the one used by the computer that you should test.

Learn mode is what happens when some component is changed or the battery is removed. When this condition is detected, the ECM often goes back to some basic parameter list to use, parameters that will assure the car will start and at least run, but maybe not perfectly at first, until the correct parameters are re-learned for the new configuration.

Why? As a car ages stuff like the throttle body gunks up, various passages don’t pass fuel and air quite as freely over time, so to keep the fuel air mixture and idle rpms to spec the ECM learns and compensates. It might have to boost the amount of gas, or decrease the amount of gas compared to when the car was new. Or increase the amount of air or decrease the amount of air.

Learn mode is a good thing. It works great as long as nothing changes. But it can cause the engine to run – esp idle – poorly immediately after changing something, or just disconnecting the battery.

In an ideal world even in learn mode, the car should still start. But alas this is not an ideal world. There’s talk here of some cars, if you disconnect the battery which resets the computer to learn mode, then the car won’t start, and has to be taken in to the dealer for reprogramming. I’ve never personally experienced that, but something like that could happen I suppose.

I have one temp sensor that feeds both the computer and dashboard. I will check this tomorrow. I really need a better ODBII scanner to see live data. It would make diagnosing things a bit easier.

Check ECU fuse 1, 10amp under the hood to see if it’s blown. If the fuse is good, then the problem might be with the engine control relay

When you turn the ignition switch to start, power is supplied to the engine control relay to open the injectors. Once the engine starts and ignition switch goes into the run position, this power is cut off from the ignition switch. The computer then closes the contacts in the relay and the computer then takes over and fires the injectors.


In the latest twist the car no longer starts with starting fluid either. It cranks and cranks but no start. I didn’t touch it as I am waiting on fuel pressure gauge adaptor. Does this latest development lend itself to anything?

There is no spark from plug wires.Battery is new and fully charged. Car only started with starting fluid a few days ago, now it does not start at all, only cranks.

FIXED. This was an issue with the new crank sensor. It was not providing spark. Putting an old (and also faulty) one in let’s the car start right up.

Well, happy new year to YOU!! And thanks for closing the loop by telling us what the final result was.


Good news

Just curious . . . was the new (and faulty) crank sensor a store brand?

Are you going to get a sensor from the dealer now?

The new/faulty CKS is a duralast from autozone. I will be buying another one off rockauto instead.

Does anyone have any tip to get the o-ring to seat properly? If I put it on with the sensor, all the way up the shaft, I can’t push it in. I’ve oiled the o-ring up but still unable to get it to sit far enough in. I can’t get the o-ring into the hole. Easier to put o-ring in first then put sensor in?

Glad you got it fixed. Thanks for the update.

I believe that the O-ring has been the problem from the time that new sensor was installed. Oiling the O-ring and the hole is necessary and twisting as you press in usually gets them in. Using the attaching bolt to push the sensor is often the problem with new replacement sensors.

Rod Knox it is currently the problem. I decided to get a replacement for the other one and this one works great… without the o-ring. You know it is seated because the magnet grabs inside. I can’t get force behind it because of the location.

The other one was not seated but was also DOA as I wasn’t able to start the car without the O-ring like I can with the new one. I am good to go when I am able to get this in. Thanks for all your help!


Are you certain that there are no remnants of the old o-ring inside the hole?

Yes, I have the old o-ring out to judge the size. It should be inside the block but I can’t get it past the opening (still). It is 5 degrees out, going to give it a go tomorrow.

My 1999 Hyundai Lantra faces a similar problem.

Starts perfectly fine every morning or whenever the engine has cooled.

If the engine is hot and I try and start the car straight after driving, it keeps cranking but will not start UNLESS I use starting fluid/spray.

After using the starting spray it starts and drives fine.

However!! The car has started to bunny hop while driving now, and even stalled on its own as I was about to park it.

Any ideas ???

Suggest to re-post as a new question @akain101 . You’ll get better answers that way. Click “new topic” at the top right after clicking “maintenance/repairs” link above.