Engine Rebuild Book Section, Did I leave anything out?

[Wayne 962]

What do you do if your engine doesn’t start? There are a variety of reasons why you might have problems. There are a few common mistakes that can be made that will sometimes leave even the experts scratching their head:

- If the starter spins and spins, and doesn’t turn over the engine, then you probably forgot to install the flywheel ring gear.

- If the starter won’t turn over the engine and is not spinning, then you may have a dead battery, or your engine may have too high a compression for your starter. Get a high-torque starter and make sure that your battery is fully charged.

- If your engine doesn’t want to turn over, take a wrench and place it on the fan belt, and try to turn over the engine slowly by hand. You want to make sure that there’s nothing in the engine or transmission that is causing it to get stuck or caught.

- The car turns over and seems to fire on one or two cylinders only. This is a common mistake, and can usually be traced back to an ignition problem. Either the distributor is not installed properly at TDC, or you may have installed the spark plug wires in the wrong order.

- The car turns over, but there is no sign of it firing. Make sure that you have both spark and fuel. Remove a spark plug and hold it close to the chassis (wearing rubber gloves) as you have an assistant turn over the engine. If you can see a spark, then you know that you probably have either a fuel delivery problem or a timing problem. If you don’t find a spark, then check your CD box to make sure that it’s plugged in. It should make a high-pitched noise when it’s working properly. Also check your ignition trigger points on the distributor. Check the dwell gap for systems that use points (1977 and earlier), and check to make sure all the sensors are plugged in on for any breakerless ignition system (1978 and later).

- To check for fuel, pull out an injector, and place it in a clear glass jar. Have an assistant crank over the car and check to make sure that you see fuel exiting the injector. If there is no fuel, check the fuel pressure in your fuel injection system. Check to make sure that none of the rubber fuel lines became bent or crimped when you reinstalled the engine. Even if one or two injectors are clogged and not dispersing fuel, the engine will still try to fire on the remaining cylinders.

- If you have an MFI car, double-check to make sure that the pump is properly synchronized with the camshaft. Having a misaligned belt will cause the fuel to be delivered to the cylinders at the wrong time.

- If you have both fuel and spark but the engine isn’t turning over, then you probably have a timing problem. The spark is being fired at the wrong time. Check your distributor orientation, and also your spark plug wires.

Anything else I forgot?

-Wayne

[Bobboloo]

Yes, I think you forgot to take the day off.

Did you catch the fireworks display at El Segundo Park ? I was there and didn't see you.

Bobby

[Wayne 962]

I live in Redondo - walked down to the pier...

-Wayne

[Roy M]

If the starter won’t turn over the engine and is not spinning, then you may have a dead battery, or your engine may have too high a compression for your starter. Get a high-torque starter and make sure that your battery is fully charged.

No expert but also check the earthing to the block - never happened to me on a Porsche but burnt myself on choke cables when I've got this wrong!

Roy

[Wayne 962]

Good point - a very common mistake...

-Wayne

[ChrisBennet]

On 3.2's (Motronic) cars:
- Engine turns over but doesn't start
no fuel, no spark
Possible cause: Speed/Reference sensor gap incorrect (should be 0.8mm) or old sensor wires have failed from being handled
has fuel, no spark
Possible cause: injector harness not plugged in. Check connector on firewall behind throttle body.

These are a few that have gotten me at one time or another.
-Chris

[Dan Owens]

Wayne,

Don't forget there are a lot of us that have post '83 cars that often get left out of info and diagnosis for starting and trouble shooting
checklist, and repair tips as well. Also in many of the non factory manuals out there the writing is really geared toward pre motronic motors. Pulling injectors and placing them in a glass jar being one example. Don't forget us!

[john_colasante]

Safety Alert!
To test a spark don't remove the original plug lest air/fuel sprays out of the cylinder and will be ignited by the now removed "test plug" being held close by. Just use a spare plug and leave the original in.

[1bar]

I had a bad socket under the rear fuel pump relay on my car - didn't get enough fuel until I pulled the relay out and wiggled it around. Must have dislodged it while pulling the engine out and / or putting it back in. Frustrating. There can be lots of reasons for poor or no fuel delivery.

Also, there is absolutely no way I'd hold a spark plug even with rubber gloves. If some poor guy thought Nitrile gloves from the box were the equivalent of an electrician's gauntlets, he'd get his pacemaker reset promptly !!

A better way to test the spark is to pull the coil wire out of the distributor cap, and then tape it up next to the fan housing with a small (~1/4 in) gap from the metal tip to the fan housing. Tape it so that it's stable. You do NOT want to crank the engine with this cable pulled unless there is a spark gap for the spark to jump, otherwise the voltage will exceed the internal insulation capability of the coil and ruin it. Now, when an assistant cranks the motor you can see the spark quite easily - if it's working

[Wayne 962]

Those are all good suggestions, thanks!

-Wayne

[michel richard]

Starter not turning could be bad wiring to it or bad ignition switch.
I doubt that fuel being delivered at the wrong time will keep a car from starting, whether MFI or any injection system. For example, on a D-jet, you can switch the injector electrical plugs from one injector to the other, and it will start: the fuel simply hangs around above the the intake valve (for less than a second) until it gets sucked in.
engine not turning could be hydraulic lock inside one or more cylinders, from fuel, water, or oil (ouch in all cases).

HTH

Michel Richard

[Wayne 962]

Ahh, you are right - with the D-Jet. However, the D-Jet (and Motronic) is a phased-sequential system which means that the injectors are not firing in conjunction with the cylinders.

The MFI system is a true-sequential system where each injector is fired with a high-pressure pulse when the intake valve is beginning to open.

This is also covered extensively in the Engine Management Section of the new book.

If you hook up the MFI pump wrong, the car will not run...

-Wayne

[michel richard]

You mean that the MFI is designed to squirt the fuel straight into the cylinder, past the opening intake valve ? which would be explained by the high fuel pressures involved.

Did not know that. And I've just put an MFI engine in my 914, was running D-jet previously.

M