Intermitant Long Crank to Start Car

Maintenance/Repairs
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Back yard mechanic here, owned the car since new, a little OCD, I take great care of everything I own. Preventive maintenance is my thing…belts, hoses, plugs, filters, etc., stuff is replaced to keep car in top shape.

The Problem: 80k miles on the car, and since it was new in 2002 it started within a second of turning the key. A couple months back, it cranked for 5 seconds before starting…and since then, randomly, hot/cold doesn’t matter, the engine will take 3 to 5 seconds of cranking to start; in between those random long cranks, it starts instantly.

Once started, idle is rock solid and the car runs as strong as ever. I log every tank of gas and MPG has held steady, so the engine is running fine.

As a test, for every start in my garage I hook up an extra battery, and sure enough, even with a second battery connected, I had a long crank incident.

While the starter motor isn’t signaling an obvious problem, it’s still suspect #1 in my mind. Agree? or is it possible some sensor has gone flaky and messed up the start?

Edit: I did suspect lack of fuel due to fuel pump/injector issue and did the “light up the dashboard and wait” trick to give the pump plenty of time to build full pressure; didn’t solve the problem.

While not as good as removing/cleaning the injectors, I did run 2 tanks of fuel that contained injector cleaner…didn’t solve the problem nor did it change MPG.

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No. If the starter turns over the engine each time you turn the key to Start, it is doing its job.

You have either no fuel or (less likely) no spark when it turns over but does not start up right away and run OK. To make sure there’s fuel and fuel pressure up at the engine, turn the key to Run, wait a few seconds, and back to Off. Do this “key dance” several times. Each time the fuel pump should run for a couple seconds then turn off. You may hear it. Finally, turn the key all the way to Start. Any difference? Good luck.

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Impossible to tell but my last guess would be the stater. Way back on my 86 park ave, I would get an intermittent extended crank. At the dealer we watched the fuel pressure gauge go to zero. It was a dirty injector.

Lots of sensors that may not be feeding accurate information to set the fuel ratio like engine temp sensor. Or sticky pump, or sticky by pass valve, etc. a computer could see what the readings are at start up, but will not be cheap chasing the problem until it gets worse. Others may disagree but crank and temp sensor are cheap.

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Leaky injectors or fhel pump check valve. Do as @shanonia suggested. The key dance will tell you if it is fuel or spark. If the dance works to give a quick start, it is fuel.

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It’s all a guess from where we sit but the consistent mpg and the strong battery/ starter suggests a possibly weak cam shaft sensor.

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Is that the coolant temp displayed on the dash or is there another temp sensor?

As a home mechanic, any opinions on reasonably priced computer to fit my needs. I don’t have one and I see prices from $20 to $1,000 for a unit.

It’s a 2002 dodge, not exactly a high tech car; how much “computer information” does it even have?

I’ll check with the local auto parts stores and see if any offer more than just a simple code reader for their courtesy checks.

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I was wondering about that but thought it would contribute to a drop in mpg and a rough idle.

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I’m not the most knowledgeable person by I thought the crankshaft sensor was the primary sensor for determining spark at speed ( when power and gas mileage is affected ) and the camshaft sensor basically told the ecu where the camshaft was at starting (???)

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Fuel pump only runs for 2 seconds doing that, try it 3 or 4 times before cranking.

EDIT: looks like @shanonia beat me to it.

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The crankshaft position sensor informs the computer whether or not engine is rotating, it detects for engine misfires, it sends the RPM signal to the tach, it determines the correlation between the crankshaft and the camshaft(s).

The camshaft position sensor sends a signal to the computer for ignition and injector timing.

Tester

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If the engine starts without running rough, you can rule out leaking injectors.

Tester

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I can’t speak for your car but for mine it is different than the one the temp gauge. There are two, the engine temp sensor feeds engine temp to the computer. Service manual showed what and where.

I think tester though is on the right track. Cam sensors srevcheap too but never had a bad one like crank and temp sensors.

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These type sensors don’t generally get “weak”. They work, or they don’t. They are pretty simple devices. Either a coil around an iron core or a hall-effect chip

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Tester

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Could be causes by several problems, but my guess is some type of fuel pump problem. It seems like you are on top of this, good for you. Many owners would just live with the longer than normal cranking. But this is a symptom that will likely result in a cranks but fails to start eventually.

Ask your shop to do a fuel pressure hold test. If the one-way valve is failing that is supposed to prevent the fuel rail pressure from draining back into the gas tank when the engine is off, this could be a symptom.

Are you sure it is cranking ok? Do you hear that rrr rrr rrr sound consistently when the key is in “start”? If you aren’t sure ask your shop to measure the voltage at the starter’s “s” terminal during attempted cranking. Should be 10.5 volts or more.

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Since I didn’t know if his vehicle had a Hall effect sensor or a magnetic one. I just called it possibly weak. Maybe not the correct terminology.
I’ve had Hall effect sensors go bad suddenly with no advance warning and leave me dead on the side of the road, which I believe is the usual case. But I’ve seen where a magnetic ( not Hall effect) camshaft sensor failed slowly (on a friends car) causing the long crank.

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You might ask your shop to do a visible test for spark during cranking. If it cranks ok but no spark for several seconds, then later a spark appears, could indicate a problematic engine rotation sensor. Generally the comments about failing crank sensors here though are that it either never works, or only fails when hot.

Placing a spare spark plug on a spark plug wire, then holding the base of the plug against a metal ground, is usually how I do that. No experience with that method on a coil-on-plug config though.

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There’s usually two sets of engine rotation sensors, one for the crankshaft, and one for the camshaft. The configuration varies from car to car. You are correct that the crankshaft position is a primary spark system input. On older design, esp one that use a distributor, the crank position is inferred from the distributor shaft position.

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I’ve had the Hall effect just leave me high and dry. And another one that was cracked do the same. No warning except a slight miss on heavy acceleration.
I

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Years ago I had a customer’s Dodge, 2.0 L engine in the shop, 8 to 10 seconds of cranking time, check engine light on and P0340 fault but the car was not in for this, I believe it was in for an air conditioning repair.

I offered to replace the camshaft position sensor and this was approved by the customer. When removing the old sensor I found the magnet that triggers the signal was missing from the camshaft, this was a remanufactured engine and the magnet was overlooked by the installer (good independent?).

The computer needs the camshaft position sensor to identify compression stroke or exhaust stroke. If the engine does not start after 10 seconds, the computer will switch what it guessed was the compression stroke timing to exhaust stroke to start the engine, after that the crankshaft position sensor provides the information needed to run the engine.

Never mind all of that, it sounds like the fuel pump is leaking down while the engine is off. Measure the fuel pressure while starting the engine.

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