got an intermittent start problem...

I can't seem to figure this one out guys...so i'm looking for some help. the 948 developed an intermittent problem, where the car would die and not restart (would crank but not fire) for about 10 minutes...then would restart and run fine until it would do it again. I haven't been able to fix it yet...i've tried replacing several things and reworking some wiring.

so far i've done this:
replaced Ignition Control Module
replaced Ignition Coil
rewired all of my computer/engine grounds

After i did all of this work, the car seemed to be fine, but i didn't get to take it for a drive, it was idling and revving beautifully, i drove it up and down our long driveway a few times, got it real warm...let it cool off, then got it warm again and it never really died. it did however conk out, but immediately restart by giving it some gas and cranking it for a few seconds...seemed odd.

the other day my dad started it and let it warm up, and it died and wouldn't restart just cranking it, he didn't try giving it gas while he cranked it, so i don't know if that would have worked.

what do you guys think this could be? i know i have pressure at the rail (not confirmed by a gauge, just by the "push the little button and see if it sprays" test)...i know i have a working fuel pump (i can hear it run...i have the fuel pump hardwired so it comes on when the key is in the on position). I also know that i'm getting spark on by the old "pull a plug and crank it with the side of the plug grounded" test. so what the hell is going on???

My initial ideas are...fuel pump could be bad (just makes noise, doesn't actually push enough fuel)...fuel filter (this probably needs to be replaced anyway, so it's first). Other than that i don't really know...maybe bad fuel?

thanks for reading the long post!
Ethan

I was just about to shout out Optispark until you mentioned that you checked for spark. Question is, when did you check for spark? Did you check during the no-start situation? Reason I ask is because my optispark had a condition where I had to crank it 8-10 times at roughly 6 seconds each for it to start...everytime!

The opti can do straaaange things. Next no start situation, do not try to start it but immediately check for spark at cylinders 2,4,3 and 5. Although, even if it does, this does not mean the opti is sending the spark at the correct time or that spark is getting to all 8 cylinders (debri on shutter wheel = low res on scanner).
Regardless, you should own 2 important tools; a fuel pressure gauge (~$35) and an OBDI or OBDII scanner (depending on year of computer).

Questions:
What year 944 do you have?
Has the fuel pump ever been replaced and if so when and with what?
What year is the engine?
Has the fuel pressure regulator, injectors or optispark ever been replaced and if so when and with what?

For fuel, You really should have a fuel pressure gauge already!!! You should either buy a fuel rail pressure gauge or drive to a place that will let you use one (maybe autozone?). What you should see without the engine running is 44 +/- 3 psi. This pressure should also be observed at wide open throttle (simply disconnect the vacuum line at the regulator to simulate WOT). As well, while the vacuum line is off, look into it and/or smell it for signs of fuel inside the line as this would suggest a faulty regulator.

Ten minutes after shutting the engine off, check the pressure on the gauge (leak down test). It should NOT have dropped after 10 minutes. If it does, this may mean that 1.) the internal check valve within the fuel pump is faulty allowing fuel to run back into the tank thus depressurizing the system, or 2.) an or multiple injectors are stuck open allowing fuel to drain into a cylinder which may cause hard starting (flooded) as well as depressurizing the system. If the latter is suspected, take the fuel rail off the intake, suspend it over a cooking pan (have rags ready), and turn the key to the run position only (do not attempt to start the engine!). If an injector is stuck open, you will see drops of fuel from a/multiple injectors which then should be either replaced or the whole set sent off for rebuilding.

To truly determine if the fuel pump is at fault, you need to see how it behaves at speed and wide open throttle in real time. To do this, remove the seal along the top of the firewall. Then route the gauge and hose through the hood and tape it to the windshield so that you can observe the pressure at various stages. If the pressure falls at any point during hard acceleration, it should be replaced. Again, you should see 44 +/- 3 psi here. A drop of 3-5 may be okay but 5 is pushing it and 8-10 is a red flag.

Other things to check:
ANY fuel fittings/adapters leaking?
Gas cap sealing (should here "whoish" when taken off).
Fuel supply line and return clear?

I did check spark during the no start condition...but i only checked it on one plug.

one small problem i have is the lack of a diagnostics port on the engine wiring harness (i accidentally left it behind at the junkyard when i removed the wiring harness from the caprice it was in) so i haven't been able to plug in a scanner to check for trouble codes.

Answers:
I have a 1987 Porsche 944 n/a
I don't know off the top of my head when/if the fuel pump has been replaced, i personally have not done it
The engine is from a 1997 Pontiac Firebird Formula
The fuel pressure regulator and injectors are original...the optispark was replaced because the engine did not come with one...it was a cheap ebay opti (this is probably the problem, but I'm really hoping it isn't...)

I do occasionally catch a whiff of gas when i start the car/run the fuel pump, so i guess i need to look around for leaks...if anything it would be a VERY subtle leak...something that could easily go unnoticed...I believe the gas cap still goes "whoosh" when i take it off after running it

I will have a lot of time over spring break to mess with the car...that's coming up next week, so hopefully i can come back here with more info at a later time!

Thanks!
Ethan

the optispark was replaced because the engine did not come with one...it was a cheap ebay opti (this is probably the problem, but I'm really hoping it isn't...)

Yeah I tried an autozone unit...lasted about 3-4 weeks....broke down and bought the genuine GM unit. Never failed since.

The fuel you smell could be from the opti not delivering spark to cylinder and the fuel is just being spat out the back. Who knows. You need to do some testin!!

One thing about the fuel pump: you should be able to hear it when it's running. Maybe your fuel pump relay is going bad??

i can definitely hear the fuel pump run when i turn the key to run...at least i think it's running...that was one of my questions, that is whether the fuel pump is actually pumping when it sounds like it. The fuel pump relay is only about a year, maybe a little more, old so i don't think it's bad.

When the engine is running well there is no fuel smell, no backfiring and no chunks of crap coming out of the exhaust (had some bits coming out before i replaced the ICM and Ignition Coil, so i think they were going anyway...)

Do you think i would be okay buying a used gm optispark unit? i really don't have the kind of money to buy a brand new unit...

i had a 94 lt1 in a trans am and the optispark went out due to debri from leaky water pump and put a reman unit on it that lasted 3 months and it went out.i finaly bought a delco unit which is still working 3 years later.the computer will read a code if it is bad.there are several options in replacing the distribiter as msd makes one.there is also a kit out there that adapts an ls computer to the lt1 with a coil on plug setup.i cant remember who makes it but ill dig out the hot rod mag i seen it in and post.check out [You must be registered and logged in to see this link.] they make a kit to do away with opti spark with coil on plug ignition utilizing A 24 pulse crankshaft relucter which alows use of ls1 coil on plug ignition

I wouldnt buy the opti until you are sure that it is causing your problem. First thing to buy is an ALDL port and wire it in. Then read the codes. The following parts are bought from [You must be registered and logged in to see this link.]

OBD2 Diagnostic Port Parts Needed:
Qty 1 OBD2 Port Plastic Connector, 16 Pin PN# 829-12110250 $1.07
Qty 6 Terminals - for OBD2 port PN# 829-12129373 $0.21
Qty 2 Terminal Lock - secures terminals PN# 829-12160437 $0.27

OBD2 LT1
Pin 2 - Serial Data - FROM the PCM.
Pin 4 & 5 - GROUND - Usually only pin 5 is needed, however some scan tools/code readers will need GROUND on pin 4 as well.
Pin 16 - 12v+ BATTERY - Power from 12v+ Battery source.
Pin 6 - Diagnostic Request/Field Output Enable
Pin 9 - UART Serial Data
1995 LT1 used an OBD2 port, but were not OBD2 vehicles. These did not have a Serial Data on Pin 2. These used pin 9.

[You must be registered and logged in to see this image.]

EFI Live has a neat idea, but it's expensive...

24x Package for LT1 and LT4
For use with 92-97 LT1 and LT4 engines with a single roller timing chain only. Package includes 24x crankshaft reluctor, 24x crankshaft sensor, aluminum cam sensor housing, 1x camshaft reluctor, and LS2 camshaft sensor. This package equips the LT1 and LT4 engines with the 24x crank and 1x cam signals required to use the LS1 PCM. $525.00

Used LS1 PCM - GM# 12200411
Pulled from a 2001-2002 GM vehicle. PCM contains the original vehicle calibration. You must reflash with the operating system and calibration suited for your application. $100

Stand Alone 24x Engine Wiring Harness
EFI Connection builds brand new engine wiring harnesses for the TPI, LT1, and LS type engines. Our 24x stand alone harnesses are built to order so that you receive the best possible engine wiring harness for your vehicle. Installation is very straight-forward with only a few wires to connect to run the engine. A fuse block and fuel pump relay is included. These harnesses are built after being ordered and have an estimated 3 week lead time. We recommend that you contact us by phone to order this harness, but if purchasing online, we will contact you to get specific vehicle requirements. $650

OR...

24x LT1 Harness Do-It-Yourself Kit
Are you a DIYer? Save some cash on the 24x LT1 conversion! This kit will provide all harness components you will need to add to your original 94-97 Camaro/Firebird LT1 engine harness when repinning it for the LS1 PCM: PCM connectors, extra PCM terminals, coil harness, cam sensor harness, crank sensor harness, and second knock sensor harness. LS1 PCM conversion instructions not included. $100

You will still need [8] LS2 coils, wiring and brackets. New will set you back about $250+ without the brackets.

Grand Total = $975 - $1525.

Ouch.

For that much, just build a Megasquirt PCM, use a TPI harness for the fuel injection, order an Opti delete from Jegs for about $60, and run an EDIS-8 coil setup from a '98 Cobra. You'll also need a 36 (-1) tooth reluctor wheel and crank sensor, and a wide-band O2 sensor. Should come in under $750 if you shop smart.

IMHO, the Megasquirt setup should be the no brainer here. The MSD is $500+, a new Opti is $3-400. The Megasquirt is infinitely tunable, open source software (constantly updated), and offers adjustable spark advance. No GM PCM offers that...not even from EFILive.

Oh yeah,
I know who has a .dxf file for the LT1 Reluctor Wheel (THE FIRST for the LT1. SBC has been done, but not for the LT1...YET...)

good job lt1 thats ussally the best check on a computer controlled vehicle is a scanner check to see if any codes are set .thats one of the best investments you can make when converting to or owning a computer controlled vehicle.considering you have the finances to afford one.most autoparts stores in my area have a scanner that they will hook up to see if any codes are set.you can spend a few bucks and have a big headache trying to guess what it is when you could have pluged in a scanner and eliminated some of the possible culprits to the problem.i know from my experince with a faulty optispark that it will run fine for a while then all of the sudden it will die and not start until you call a tow truck then when it arrives itl fire right up lol.speaking by experience.also when my opti spark failed it would idle and rev fine but when id drive it and put it to the floor it would fall on its face.but would run fin normaly cruising.and would run fine for 2or 3 days then just die and not want to start until you let it sit for 30 mins or so.megasquirt sounds like a no brainer to me good call greg

WOWWWW!!!


Great info guys!! i'll get on it asap and update soon!

Thanks!
Ethan

just ordered a fuel filter and all of the parts listed by 944-LT1 to hook up an ALDL, should have some results early next week...pray to the car gods with me guys!

have you checked the fuel pump / filter

also checked your cat

something like this happened on my 1995 dodge ram 1500

my cat is a new magnaflow high flow cat, hasn't been on the car more than a few months....i have a sneaking suspicion that this is all because of a bad fuel filter. I have one in the mail coming from pelican parts, hopefully it should be here early this week, so i can get that replaced and see if it makes any difference.

good to know that the fuel filter is in fact a possibility here.

also, just for those interested....
last night i spent some time messing with the car, she started up on the first crank, but died quickly (didn't like the cold i guess). With a little gas i kept her running for a few seconds, and then the idle smoothed out and she ran nicely. I let her get up to temp (about 195-200) and she stayed there nicely for a while. Then i shut it off and let it cool off for a while...when the engine temp was at about 160, i started it back up...started on the first crank and ran better than i think it ever has. Let it idle for 10-15 minutes then shut it off and let it cool for a little while.

This is where it gets weird...i went back out when the temp was back down around 150-160 and tried to start it...it just cranked and wouldn't fire. I went back inside, came back out less than 2 minutes later and it started like nothing had happened.............weird huh!

hmmmm. That is weird. Have you bought a fuel pressure gauge yet?

Turn the key to the on position and pull off the vacuum line to the FPR. Any gas there at all?

Next time it wont start, grab some starting fluid and spray it into the TB.

IAC?
Maybe as simple as the charge indicator connection, or even a bad alternator.
Any codes?

Try this:
LS1Tech - LT1 starts, but won't run

FWIW, LT1s are "voltage-sensitive". IAC, control module and Opti require proper voltage for reliable operation. I also remember a PHB post about exciting the alternator...
Think it was Doug.

interesting...read the whole thread.

looks like a low battery charge or an alternator not charging at the right time could do it...do you think a bad battery might singlehandedly cause my issue? My dash gauge reads around 14 volts when the car is running well, but often when i first get in and turn the key, it reads down near 11...seems like this might be a problem according to that thread. I have a brand new high output alternator (powermaster brand, it's a nice one...) so i don't think that my alt is bad.

I haven't gotten the port to hook up a code reader yet, hopefully it will come tomorrow or tuesday, i'll check for anything interesting then...

I may have a problem with the IAC, but i don't think it's causing the no start, i think it's causing the difficult cold running. When the no start happens, i can give the car any amount of gas and nothing changes...it looks like a no start/hard start from an IAC can be solved (to a certain extent) by keeping your foot in it a little

Got the ALDL hooked up...plugged in a code reader. at first it didn't throw any spark related codes, but that's because it was running. When i got the engine to die in the previous fashion, i plugged it in and cranked it with the code reader hooked up. it threw a P1371 code, which translates to an opti going bad.

So, i went up to the local pick-n-pull, found an opti on a 96 roadmaster...pulled it (paid 24 bucks btw) and spent the next 6ish hours pulling everything off of the front of the engine and replacing the opti, then putting everything back together.

got it all buttoned up, turned the key and it just cranked...there was some odd popping in the midst of it cranking, but it didn't fire (i figure the popping was the exhaust valves opening to release the air in the cylinders. I tried spraying starter fluid in, didn't do anything, just cranked...so there's still no spark.

My two ideas are that the opti is pushed too far in to the engine (i noticed that the opti didn't really want to go completely flush with the mounting tabs where the bolts go), so i'm going to try putting a couple of washers in and spacing that out. I also think that the pcm probably still has that code stored, and is disallowing the engine to spark because it still thinks the opti is bad.

now my only question is...

did you install the opti correctly? If it did not push in all the way you probably missed the key way and it's not firing because the distibuter is off mark. The distributer cover needs to be off an opti to correctly install it since it likes to wander during install. Also do yourself a favor and go to kragen/oriely and buy a whole front seal kit and replace the seals since your gonna be taking it apart again. It costs a whopping $14 and has every gasket/seal you need to replace the timing chain (which you are not doing so you will have 1 extra timing cover gasket). The long deep slot is where the dowel goes. Boy there was all kinda things wrong with that statement..........

the seals on the front of the timing chain cover are all new...made that mistake once already! I have a feeling i didn't get the opti quite right, or that the lt4 cam's dowel is too long and the opti doesn't fit over it...

we will see!

IIRC LT4 hotcam dowel is the correct size for a 94-96 (I don't remember having to hammer the dowel down on my old hot cam) but will not work on the older setups.

I want to hear your exhaust when you're done.

well it turns out i hadn't installed the new opti correctly...i got it all torn back down, and put the opti on correctly, cranked it and it fired on the first crank...so yeah, it was the opti all along.

I'm still planning on replacing the fuel filter tomorrow, but i'm really excited to have a running car again!!

thanks for the help guys!!!

Excellent job tracking it down!

the cam post wasn't aligned exactly right in the slot of the distributor, so i wasn't getting proper spark. That is all!

the opti should have been named the optimistic distribitor lol.good job.glad you figured it out