gizmoe107

Having a problem with cold start on my project ’83 944 (non turbo). By cold start I mean first time each day – not necessarily air temp.

I know there have been many threads before this one concerning starting issues and I believe I have read all of them. Any suggestions are appreciated at this point!

I can get it to start by giving it a shot of starting fluid. Once it starts it runs fine and after it warms up it you can turn it off and it will start up again. That makes me think it is a fuel problem.

Short history - I acquired this car several months ago. It had not run in 6 years. The previous owner was experiencing intermittent start issues which caused him to stop driving it on a daily basis. It had no spark and no injector pulse. By replacing the speed and reference sensors (connectors were crumbling) I was able to get spark and injector pulses. 3 of the 4 injectors had no fuel output. Cleaning the injectors took care of that problem.

Here is what else has been checked/replaced:
Compression is 175 – 180 psi
New distributor cap, rotor, wires and plugs
Drained gas tank and refilled with fresh premium
New Fuel filter
Timing belt and balance shaft belt replaced
Checked mass airflow sensor
Checked mass airflow temp sensor
Replaced DME engine temperature sensor
Checked auxiliary air valve
Found and fixed vacuum leaks – including resealed throttle body
Checked throttle body switches
Fuel pump pressure 29 psi @ idle, 35 psi with vac hose disconnected
Fuel system leakdown - 30 min after shutdown fuel pressure has not dropped 1 psi
Fuel pump volume - 1600 cc in 30 sec
Cleaned ground straps that back of engine
Re-soldered the upper board in the DME computer

2 items seem kind of funky to me. First - idle speed is high. By turning down the brass idle screw to ½ turn from seated I can get the speed down to 900 rpm. But according to the reseal kit instruction it should be closer to 2.5 turns from seated – which gives a little over 1000 rpm. Second – if I pinch the return hose closed the fuel pressure shoots up to 80 psi. Supposedly it should be no more than 58 psi. I replaced the fuel pressure regulator but the diaphragm started to leak. The 2nd FPR has the same pressures when running. I hesitate to pinch the return line completely closed (I wonder if that’s what ruptured the diaphragm in the first FPR?) but the pressure starts to rise over 58 psi as soon as the line is pinched.
According to Clark’s, if you disconnect 1 injector and the engine starts the fuel pressure is too high. I did that once and the engine started but of course ran like crap until the injector was plugged back in.

Is this a fuel problem? Why is the idle so high with idle screw at 2.5 turns? How is the FPR supposed to work?

gizmoe107

Any ideas? I find it hard to believe that a car that runs as well as this one cannot start on its own without the help of starting fluid. Not to mention how embarrassing it is to have to pop the hood every time I get ready to leave.

william_b_noble

look for a vacuum leak, that would explain the high idle and the non starting - a cracked J-boot, for example, or a badly cracked hose. The fuel press regulator requires vacuum to know what pressure to go to, so that's consistent with low vac.

gizmoe107

A vacuum leak makes sense - I have already found and fixed several vacuum leaks, including a large one in the J-boot. I have been checking for vacuum leaks by putting a 2" pvc cap in place of the AFM and pressurizing the system to 5 psi. I still have air blowing out the oil filler cap. I was assuming that was coming out of the pvc system - is that correct? Or should I be able to pressurize the whole intake with no leaks?

konakat

You should expect the fuel pressure to go up if you pinch the line. The FPR works like a blow-off valve to relieve pressure in the fuel system. If you pinch off the return line then you are preventing it from relieving the pressure. Your pressure numbers sound fine.

I wouldn't put too much stock in the number of turns for the idle screw, it is a very sensitive adjustment. On my car a half turn is about a 100 rpm adjustment, so any minor variations in your car could result in big differences in the number of turns.

You should run Clark's leakdown procedure. It sounds like you could be losing fuel pressure while the car sits so the pump ends up having to prime before it will start. This would either be caused by a fuel leak or a bad check valve at the output of the pump. To do a simple test of this theory, you could jumper the DME relay then see if you can start the car cold. This would force the pump to run for a bit before you turn on the car, building up pressure in the fuel rail.

mytrplseven

I vote for a bad check valve in the fuel pump also.

gizmoe107

Finally Fixed! After tracking down every last vacuum leak (at least that's what it seemed like), the cold start problem was still the same. The only thing left was the DME computer. Bought a guaranteed used one of of eBay and fixed the problem! Just wanted to follow up in case someone runs across this thread with the same issue in the future.

mel_t_vin

Well done.

Thanks for closing the loop.

teleloco9

do all 944 have dme computer or only the 85.5 and up cars had a dme relay and computer and the early cars just had fuel pump relay? my 85 started doing this yesterday, starts great when warm and driven finiky after cool down. i'll check the fuel pressure and leakdown as per clarks.....but wouldn't 20 seconds of cranking repressurize the system if there was a leakdown issue?

mel_t_vin

All cars had both a DME and DME [fuel pump] relay.


Go back and take a look at Gizmoe's [extensive] checklist in post #1. If your background/problem sounds similar, simply swap out your DME with another 944/1 and see if that resolves your issue.

teleloco9

turned out to be fuel pump relay, when i cracked the fuel rail cap there was zilch, put in spare relay and fired right up, and again this morning. the old relay wouldn't click over with a 9v battery so i think it is the culprit. time will tell.......

mel_t_vin

Well, that was one of the most inexpensive fixes you'll come across during your long and storied ownership. Nicely done.

BTW, the OEM DME relay is not expensive [~$30]. Pick up a couple and keep one [or the DME relay jumper] in the glove box at all times.

teleloco9

i ordered another spare relay last night after i plugged the spare in, $27 + shipping from partsgeek. i also got paranoid after surfing some posts about the dme computers failing around this timeframe so i ordered a spare ecu this afternoon with an autothority chip.....so the fix became a little more expensive......it was really an excuse to run with a chip since i've been dying to see what the chip does to the low end torque and mpg but those old ecu's are not easy to chip so i never did. plan is to put my existing ecu into storage as the spare if the chipped is an improvement........which i assume it will be since there's plenty of room for improvement

mel_t_vin

Unfortunately, there's not as much room for improvement in your '85, as you assume. I suspect you'll see single digit hp/tq at the wheels.

Re: picking up a spare DME relay...wise choice.