hard to cold start

kayw · 03-18-2004, 11:05 PM

Just have a problem on my 944 S2 (1989) that it is difficult to start up (cool start) . Hot start is fine.

When the engine is cold (no the weather in cold) , usually the first try must fails. Then wait couple seconds, start again. The engine starts after 4-6 crank. Never success to start in the first try.

Sometimes it wouldn't start even forth or fifth try... need to wait for a hour and try again.

When engine starts, everything is fine -- idle speed is stable, pickup and acceleration are good.

Just difficult to start at when engine is cold.

Fuel pump works.
No air leak in the intake.
I also clean the in take and throttle too.

Since the car runs in good condition. Therefore I don't think problems in fuel pump or air flow metre

I check the forum... people mention it may relates to fuel pressure regulator. Is it true?

One more question. I hear some noise from the centre guage (air condition outlet) at "key on". (Is fuel pump located?) What is it?

Thanks very much!!

kayw · 03-18-2004, 11:09 PM

just add some more information.

Somebody works in Toyota mentions that the fuel pump may cause cold start fail because the fuel pump doesn't hold the fuel pressure over night. Therefore, hot start OK because the fuel pump still keeps certain pressure for a while (ex. a night)

My car is 944 S2 NA (1989)

Thanks!

Kay

pokey · 03-19-2004, 01:38 AM

Noise with key on is vent fan, even when "off", it is still on... albeit very low speed.

Makis · 03-19-2004, 07:04 AM

First of all the S2 will need a few cranks to start anyway irrespective of cold or hot. If it start quickly when hot i.e starts after the first crank then the possible problem you have is leaking injectors. They leak and starting mixture is higher then normal and the car may actually start quicker when hot. A leaking injector can cause poor cold start problem. This is because the fuel leaks out the fuel lines into the engine and fuel pressure goes down needing more cranks to bring it back to normal operating pressure. Try some injector cleaner before you attempt taking them out to clean them proffetionally.

kayw · 03-19-2004, 07:30 AM

Hi, thanks for reply. Tonight I still have trouble to start the car. Try about 4-5 time... each time try 3-5 cranks (because I don't want to harm the starter and battery) and it runs finally (& luckily). Usually once the engine is fired, I must push little gas otherwise the engine will be off immediately. Then keep giving gas for 3 - 4 seconds, release the gas panel, and the engine runs smoothly at idle. Then the car runs perfectly. About hot start, it wouldn't start "immediately". It still takes 3-4 cranks, but engine starts at the first try. No need key off and start again (and again again, like cold start) Any idea? Thanks!! PS. I am living in Hong Kong. No sure any difference with an US 944 S2 Thanks for all of you guys, and please forgive my poor English. Kay

Makis · 03-19-2004, 08:02 AM

It sounds like you just got hold of this car. I would not worry about the starter. I would use the starter for at least 10 seconds when cold before you stop the starter. You may just find out the car will start first thing. Once you get used the way an S2 starts you will not worry about it again. When I got my S2 the starting issue was the first thing that puzzled me. Enjoy S2 Porsche ownership.

kayw · 03-19-2004, 09:26 AM

to Makis and Pokey, thanks for you guys' reply. I own this car for 9 months. Before this Porsche, I owned a Nissan sporty car, which had a similar "cold start / fail to start" problem. For that Nissan, the problem caused by a bad regulator. Therefore, I have same though on the 944 S2. Tonight I try seeking more details. I turn key to ON (but not start) I couldn't hear fuel pump noise. After the engine fired (of course, after starting couple times) I hear the fuel pump works! My question is -- does fuel pump not pumping fuel at key-on? Once start the engine ... crank--crank--crank-- then the fuel pump operates? Or, it is problem of the fuel pump or relay? Just want to make sure is it normal or not. I don't mind to crank couple times to start the engine, but I am afriad the engine still not be fired after couple try (I experience this three times. Each time I just leave the car 30 mins and try again.... ) Thanks!! Kay

kayw · 03-22-2004, 08:11 PM

Hi,

I start the car (944 S2 1989) in the morning. It wouldn't be started. I have tried 6-7 times -- each time I crank for 10 seconds. Nothing ..

Starter works. Oil level OK. battery OK.

Then I catch bus to office.....

When I turn "key-on: I didn't hear noise from fuel pump. Is it normal?

What diagnosis / repair I should do?

Thanks very much.

Kay

pokey · 03-22-2004, 10:16 PM

Kayw, you're English is much better than a lot of native English speakers I,ve dealt with! Yor fuel pump will NOT run with the key in "on" position, you must crank the engine for the pump to run. I would check the fuel pressure, and the pressure regulator/ damper. Good luck!

kayw · 03-23-2004, 12:21 AM

Hi, thanksPokey! How do I check both fuel regulator and damper?

Just in case, if they need to be replaced, is it better to replace the DME relay too?

Thanks.

Kay

pokey · 03-23-2004, 09:19 PM

You'll need a fuel pressure gauge, it connects to the forward end of the fuel rail. It sounds like your DME is OK, but it is a good thing to carry a spare one.

kayw · 03-24-2004, 02:51 AM

Thanks Pokey. I've ordered fuel regulator and damper, plus a DME. Hope the problem solved after replacing them, (and not a bad fuel pump... I am scared ...)

I will go for 2 weeks trip. Probably I do the replacement during Easter. I let you guys know soon.

Thanks.

Kay

DannoXYZ · 03-25-2004, 03:58 AM

Save your money on the DME. Check your engine-temp and air-temp sensors. These tell the DME how much extra fuel to add for cold-start enrichment. Also make sure your TPS is adjusted correclty.

kayw · 04-10-2004, 06:28 AM

Hi, where is the air-temp sensor located? Is it = air flow metre ?? Thanks. Kay

ae1969 · 04-10-2004, 07:48 AM

bad temp sensor can cause a hard cold start..... but normally will not cause a complete NO start..

DannoXYZ · 04-10-2004, 02:33 PM

A bad engine-temp sensor would cause a no-start situation. It's simply a binary on/off trigger that tells the DME whether the engine is cold or not. You can test this yourself by just unplugging the engine-temp sensor near the front of the block (has blue injector-type plug).

A bad air-temp sensor on the other hand (located in the AFM-airflow meter), is used to determine how much extra fuel to add on a cold-start (one that's been determined by the engine-temp sensor).

Depending upon how cold the air is, a variable amount of extra fuel is added on top of the 14.7:1 stoich. mixture. On really cold days, it may add up to 26% more fuel. That's because colder air doesn't vaporize and dissolve fuel as easily as warmer air, so most of the fuel goes straight through as liquid and doesn't even burn. Hence the white smoke & steam you get on cold days that smells like raw fuel.

The lack of air-temp correction for cold-starts is the main reason MAF-kits that do not have air-temp sensors to replace the stock one have such a hard time in cold-weather with cold-starts.

Evan_944S · Evan_944S's Garage

I have experienced a similar cold start problem with my 87 S for over 2 years now. I've replaced the injectors, damper, regulator and check valve with no relief. The hard start problem seems to be humidity related (I live in Florida). Currently, during our ultra dry time of year, the car cold starts instantly on first crank. When the humidity gets higher, it will take several cranks before it finally starts. Once stated, it runs normally. When warm, the car always starts instantly -- first crank. I now consider it an electrical issue, perhaps a relay?

Makis · 04-11-2004, 05:55 AM

Quote:

Originally posted by Evan_944S
The hard start problem seems to be humidity related (I live in Florida).

I would say electrics may be at fault if humidity is an issue. Worth checking distributor cap, rotor, ignition circuit, contacts, ignition leads, ground connections, etc.

Evan_944S · Evan_944S's Garage

Quote:

Originally posted by Makis
I would say electrics may be at fault if humidity is an issue. Worth checking distributor cap, rotor, ignition circuit, contacts, ignition leads, ground connections, etc.

I've been through ALL of that. It's really a mystery. The car always stars though, so it hasn't been a critical issue -- just a nuisance.

kayw · 04-11-2004, 10:02 AM

Yes, I agree with Evan_944S. I drive a whole day - cold start at home, then drive 50 km to a shopping mall, stop the car, watch a movie, start the car again after 3 hours, drive another 50 km to home. Then I start smoothy and go supermarket tonight (the engine has cooled down already) , and nothing bad happens today.... But I don't know when will it be nuisance again.... Anyway, I have ordered a fuel regulator, damper and DME from Pelican. Just replace them since they all look so old. Also, I test (and clean) the temperature sensor and distributor parts too. Maybe they are the causes. Thanks for all help. If my car stop firing again, I let you guy know. Kay