1988 Porsche 944 won't start

misslissa2005 · 04-01-2007, 08:11 PM

I have a 1988 Porsche 944 that won't start. I just replaced the engine in it. The timing is definitly right. It is turning over but it won't start. It backfires and blows the airbox off. I've checked all the obvious and can't seem to figure this out. Does anyone have any ideas?

badjones · badjones's Garage

Usually a sign its firing at the wrong time or maybe ( hope not ) some of the valves do not close anymore. Hope it turns out to be something simple. Good luck. B.J.

blown 944 · 04-01-2007, 10:05 PM

Just look at the mark for your cam cog and make sure it is aligned with the mark ....then look down at the crank to see if it is also at TDC then check where the rotor is pointing ...(should be close to #1 wire position) and make sure the wires are in the correct order.

Even if there is a bent valve it will start and just pop a little though either intake or exhaust

You could rule that out if you start on 1 an do a leakdown test then go through the firing order to check the cylinders seal. Just use a fitting that is for a compression tester and attach it to an air source. If it is on TDC on that cylinder it should just blown a little into the crankcase. If it is coming out in other areas (intake or exhaust)to a large degree you either have a mis timed camshaft (hopefully not) or some bent valves.

Or I suppose you could have head, block or Head gasket issues if it comes out the coolant overflow.. although I would rule that out as cause for any type of intake pops.

SoCal Driver · SoCal Driver's Garage

Zundfolge

Razorback1980 · Razorback1980's Garage

Possibly the plug wires not in the correct order. When my car had bent valves, it wouldn't start at all and it would spin over really fast because it had no compression. Timing is set by the computer and isn't adjustable except through the timing belt and hopefully that is on correctly or you have bigger problems now.

Pull the number one spark plug and bring it up to top dead center using a wooden dowel rod and at the same time making sure your cam gear timing marks are pointing at the alignment marks. After it's at TDC, then pull the distributor cap off and make sure it's pointing to number one plug wire. After that check your plug wires to make sure they are in the correct order.

Here is a resource you can check out to help.

www.clarks-garage.com

1988_944 · 04-02-2007, 12:56 PM

Check the timing, TDC and Cam mark. Check that the spark plug wires are correct order, then for a spark. Check for fuel.

todd84944 · 04-02-2007, 08:59 PM

Where are you located??? There might be some folks near that can help.

misslissa2005 · 04-04-2007, 09:02 PM

I've checked pretty much all of that already. The valves are not bent nor are they sticking. The plug wires are fine. All the timing marks are lined up the car is definitely in time. The belt is tensioned and it is not jumping time either. The car is getting fuel. I put my thumb on the plug holes and it blew my thumb off when it was cranked over with each of the plug holes. I have not got to check the compression with a tester yet. I recently put the engine in the car. I had the ignition timing sensor off of the bell housing and ?I'm wondering if it might be an issue with the timing sensor. I read once that the depth had to set on the sensor. The timing sensor thats on it is from an '87 924s with a 2.5 in it. The one that was originally in the car broke. Anymore ideas?

nynor · 04-04-2007, 09:28 PM

is the rotor misaligned?

misslissa2005 · 04-04-2007, 09:32 PM

Theres an allen head screw that goes into the rotor button. I'm under the impresson it can really only go one way.

nynor · 04-04-2007, 09:44 PM

backfire through the intake means one thing: the cylinder is firing while the intake valve is open. timing is off somewhere, or valves are bent and stuck open.

misslissa2005 · 04-04-2007, 10:13 PM

So there is no way it can be the ignition timing sensor? The valves are not bent. Could there be something wrong with the cam causing it to do that. The engine is definitely in time. All the timing marks are lined up properly.

SoCal Driver · SoCal Driver's Garage

Must be one huge thumb to reach down the recessed plug holes and cover up the spark plug's threaded hole.

Nynor has it. To get back fire through the intake an intake valve has to be open and there has to be fuel in the cylinder when the spark plug fires.

Find a good mechanic and tow it there.

nynor · 04-05-2007, 11:01 AM

Quote:

Originally posted by misslissa2005
So there is no way it can be the ignition timing sensor? The valves are not bent. Could there be something wrong with the cam causing it to do that. The engine is definitely in time. All the timing marks are lined up properly.

yeah, there could be something wrong with the cam: its out of TIME!!!

Schumi · 04-05-2007, 12:10 PM

As SoCal said, it's even stamped right on the cam tower.

Zundfolge 1 – 3 – 4 – 2

if you are off by 1 it will fire while the intake valves are open and blow the air box off. If the wires are in their right spots then check that the rotor is spinning correctly and aligned..

The firing order is the only other thing besides hte cam being totally off time.

nynor · 04-05-2007, 12:28 PM

^amen.

1988_944 · 04-05-2007, 03:30 PM

When you say all the marks are lined up, are you sure that #1 is at TDC?

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by Schumi
....
The firing order is the only other thing besides the cam being totally off time.

Or a bent valve. But then the thumb says there is compression....

nynor · 04-05-2007, 03:57 PM

is anyone else suspicious about the rash of posts along these same lines? from newbies?

SoCal Driver · SoCal Driver's Garage

Unless it's obviously a troll I give all a bit of courtesy. We all came here because of problems we could not figure out on our own. As long as those asking for help give the diagnostics a try I'll mostly hang into the thread. If not then I find some one that can take direction.