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Engine cranks but won't start - diagnosing - did the search


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Hi everyone - a newbie here - any help & advices highly appreciated! This post is only for people that like to read as I try to explain everything as accurately as I can. Sorry for my English as well as I might not be that good when using mechanical terminology. Also I did search the topic but almost every one of them is different issue. Hopefully my description will shine some light on my problem.

 

Unfortunately my Boxster 986 2.5 1998, automatic has another problem after changing few months ago fuel pump relay ( checked it now as well and it clicks, tomorrow will do more checks to relay) which stopped the car from starting last time.

 

Right now I'm looking for advices on how to diagnose what is the problem and fixing it properly and preferably cheap.

 

So here's the back-story:

After driving to cinema for a mile or two and stopping at gas station for some snacks (no fuel tanking then). After I got back in the car, started it it drove for 10-20 meters and died. Another 3 attempts started a car for 1-3 seconds after which it died. I left it overnight and the next day the car would not start again.

 

Here I need to mention that few months back I replaced fuel pump relay and everything seemed ok. Just from time to time there was a weird noise at start which gone of after 1-2 second that sounded like a squeak. Also the car from when I got it for me started always a bit harsh but I thought all Boxsters do (here's the youtube video of after AOS replacement showing the sound
). But it was very smooth. Oh... one more thing: around a 2-3 weeks ago it was vey cold -15 celsius. My car stands outside. In the morning it looked like the battery died at night but the car started (slow - like in winters usually) but started and been ok. Also, but that might be my imagination I think that after one of those starts and heating the car (leaving it for 5-10 mins running) my fuel consumption went oddly high - but that might be my imagination because after that I only drove urban.

 

So here are my few ideas - if anyone would like to advice on how to rule them out or show me what I'm doing wrong, please do.

 

1. First thought is Fuel Pump that just died (18 years old car). Because when the car died I could turn it on few times for 1-2 seconds, but next day it just turns (cranks) but won't start. Well that is shot in the dark but seems logical to me. I tried to check the pump my own way before reading anything about it. So I unplugged the battery and tried to give 12V from small battery (7Ah). There is no sound from the pump whatsoever. Also connected the battery back and checked the electrical plug that goes into the pump, tried to start the car while checking the voltage on it (as I thought it should give 12V), there was none (but my friend said 12 V will go only go to the pump once to make adequate pressure and then again after the car starts...)

2. Crank sensor - but what I read here it seems like the car should start on cold engine. I will be checking it tomorrow with ohmometer (like described in different thread).

3. All other sensors (I read that there is quite a few that can make car won't start issue).

 

What I'm about to do now is (regarding to advices on forum): check the crank sensor, try to push the gas pedal all way down while trying to start, try to check the electrical circuits. Might try more as I'm still going through the threads to find possible solving.

 

I am shooting in the dark but my point is to diagnose the problem properly before starting to madly exchange parts. 

 

Unfortunately going to competent mechanic seems right now out of reach. As when I had AOS problem when I bought the car 3 of them tried to tell me my engine needs renovation (few thousand bucks), but after this forum, youtube I decided to take a shoot with changing AOS which solved big smoke problem without big expenses.

 

Also I am bit restricted as right now to small garage and the only way to get under the car is to lift up the side with provided "lifter" (the one u use when changing the wheel).

 

Big thanks in advance to anyone contributing and I will try to put as much photos as I can of my diagnostics.

 

Best Regards

Pawel - proud user of Porsche ;) Love my car - Begging for help ;)

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Check fuses C1 to C4 and E1. Is the tachometer needle bouncing a bit when you crank?

Have you tried cleaning the throttle and the idle stabilizer valve (power it on with a 9v battery to make it turn while cleaning)?

Can you verify sparks?

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Hi.  I believe that hooking up a Durametric to your car and providing the fault codes would be the most appropriate and economical first step in resolving the problem with your car.

 

 

I am shooting in the dark but my point is to diagnose the problem properly before starting to madly exchange parts. 

 
 
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Check fuses C1 to C4 and E1. Is the tachometer needle bouncing a bit when you crank?

Have you tried cleaning the throttle and the idle stabilizer valve (power it on with a 9v battery to make it turn while cleaning)?

Can you verify sparks?

I checked the fuses C 1 to 4 are good - I will check the E1 today.

 

Ok, so I will try to find tutorials on cleaning those elements and how to verify sparks. You need to get under the car to do that, right?

 

As to Durametric, well in other similar topics it didn't show any fault codes - but will order some cable today - it will always be usefull.

 

Now getting back to fuel pump. How to diagnose it properly in this situation ( I don't have special tools )? Did I diagnose it good with giving external 12 V?

 

And one big question about the parts - what are differences in fuel pumps in Boxsters - if a different made (for different car) fuel pump is same size (mechanical metal part) and provide same 4bar pressure it should fit, right? I could switch the metal element into plastic from my car.

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Hello again,

 

Firstly thanks for the advices.

 

I did something else first. Checked that there is 12V on the electric cube that goes into the fuel pump on ignition (there was) and checked that after giving outside 12V the fuel pump doesn't start.

 

So me & my friend got the fuel pump out (it took us a bit of time but is fairly easy). After that we noticed that "whirls" in the pump goes pretty rough. We gave it a 12V and surprisingly it started working but after disconnecting and adding 12V it didn't go - a wee light tap with a screwdriver to the metal outside of the pump made it start again. So our guess it's not working (blocking, not going every time like it should) :) yay - smart, isn't it? 

 

Now the big question is - probably my Boxster had this changed before (some idiot was doing it as he left a plastic part from old sender unit inside the tank - lol) - I am looking for a new pump but don't want to buy the whole one just the metal inside. I was looking all over Internet and that's what I found:

 

* The symbol on my pump is 1HO 906 091C (found only one in a shop somewhere in UK offering pump with that symbol saying it's for 2.7 Boxster - mine is 2.5 Boxster)

* Found substitutes (from reputable companies) but all they mention is 1 HO 906 091 (3 bar) - anyone knows what C stands for??? as I also found lots of same codes with A, D etc. that should fit other cars.

* Mine had Vw & Audi symbols on it which I guess means Porsche don't produce them them selfs but orders them from VW Audi.

 

So if anyone could tell me what minimum pressure should 2.5 Boxster fuel pump operate. I guess if it's a bit higher the fuel pressure regulator will deal with it but it can't be lower.

 

Once again all help is highly appriciated.

 

I will post some photos from the whole operation when I get them online as I think I can't do it here, I need an pic url.

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A little update - the letters stands for pressure D is 1.2, C - no clue. No letter should mean universal (3 bar) - if to high the regulator will lower it. Right?

 

and it states if it's multipoint fuel injection or monopoint fuel injection...

Edited by pawelkrystek
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I did get that! :D

 

I guess some communication problem sneaked in ;)

 

MY2001 - for model year before 2001 ;) right? Will do that for sure :D

 

Just didn't get MY2001 - what it means before - sorry

 

Still anyone...

 

1HO 906 091C - what C here stands for?

Edited by pawelkrystek
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Good detective work. Don't know about those vdo part numbers but it seems like you need more than 3bar

http://986forum.com/forums/210826-post7.html

Yup, sometimes Batman & Sherlock Holmes wakes up in me :D

 

Thanks for that - I will try to look for a 4 bar fuel pump than - that should fit perfectly. Also I found a full pump with plastic covers stated that is for 986 Boxster and it said it's 4 bar.

 

Thanks again!

 

P.S. - looking at it right now and it seems no shops offer those in 4 bars version :( :( :( will look more

Edited by pawelkrystek
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Hmmmm...

 

Seemed I found a perfect one (it looks perfectly the same) - working pressure 3-4 bar, but the flow is 80L/h which I'm worried is too low. I'm not sure I'm doing math good but:

 

80L / 60min = 1.3L / min = 1333cc/min - with what is in the post it should be 850cc/30sec x 2 = 1700cc/min

 

So I a way of deduction it should be at least 110L/h - the flow... right?

 

Although using different calculators show that  65L/h shoud be enough - I'm really confused now...

Edited by pawelkrystek
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850cc/30s = 102L/hr

With such a critical component, do you really want to take the risks of using non OE? My frd has a car whose ngine shut down on a busy highway with other cars zooming by. Near dealth experience. I opened up the fuel tank and found the fuel pump assembly broken dangling inside.

Edited by Ahsai
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Hi again,

 

So I got some reply's from the shops I made inquiry's in.

The UK shop (merlinmotors) after contacting supplier about spec for pump IPT312 (Sytec) was given info that other pump IPT331 should be fitted into Boxster according to their catalog.

After exchanging few emails and providing them photos of the fuel pump I took out of my Boxster they contacted Sytec again and they agreed that it is the same as IPT312, so the shop provided me with the specs that actually match what I need for Boxster. Here are the specs:

 

PRESSURE (BAR) FLOW (LTR/MIN) AMPS

1                                3.25                   5

2                                 2.8                  5.5

3                                 2.5                  6.2

4                                 2.1                   7

5                                 1.75                 7.3

6                                 1                       8

7.2                                0                      9

 

I also looked at custom pump that probably could fit from deatshwerks (the specs are obviously higher) but it's mostly for track or modded cars.

 

If anyone have any ideas or objections please speak them out. I'm posting it here just so someone can check the specs they need.

 

Kind Regards
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"probably my Boxster had this changed before (some idiot was doing it as he left a plastic part from old sender unit inside the tank - lol)"

 

 

 

The only advice that I can give is to be sure that the pump that was in the car and which is now broken was the correct one, i.e. not replacing the wrong spec pump with the same wrong spec pump !

 

Good luck. 

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"probably my Boxster had this changed before (some idiot was doing it as he left a plastic part from old sender unit inside the tank - lol)"

 

 

 

The only advice that I can give is to be sure that the pump that was in the car and which is now broken was the correct one, i.e. not replacing the wrong spec pump with the same wrong spec pump !

 

Good luck. 

 

 

Ohhhhh... I forgot to make this clear. 1H0 906 091C is the pump from Boxsters, I don't have access to information from Porsche but multiply ebay auctions offering pump with code 1H0 906 091C from crashed cars suggests that it is the one mounted in Factory (eventually after warranty service centers). It's always 1H0 906 091C!

 

By the way - on few forums no one actually could provide me with right specs for the fuel pump... The closest was Ashai with his calculations taken from other internet posts, that is at least 4 bar, 102 L/H.

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