Occasional difficult starting
Thread Starter
Pro
Joined: Jan 2005
Posts: 612
Likes: 0
From: Centennial, WY
Occasional difficult starting
My car is a 1987 S4 with five speed.
I've noticed of late a difficulty in starting the engine. This does not happen every time; just occasional. Not a whole lot I can say about the problem other than the fact that the plugs are new as well as the "brain". I don't normally drive the car in the Wyoming winter but the weather has been pretty warm so I've been using it for the last couple of days.
A small squirt of ether always starts it back up.
At 79 years of age I don't do my own maintenance anymore but I thought I would get some opinions from the experts before turning it over to my mechanic. Any help would be appreciated.
I've noticed of late a difficulty in starting the engine. This does not happen every time; just occasional. Not a whole lot I can say about the problem other than the fact that the plugs are new as well as the "brain". I don't normally drive the car in the Wyoming winter but the weather has been pretty warm so I've been using it for the last couple of days.
A small squirt of ether always starts it back up.
At 79 years of age I don't do my own maintenance anymore but I thought I would get some opinions from the experts before turning it over to my mechanic. Any help would be appreciated.
Team Owner
Joined: May 2004
Posts: 31,233
Likes: 4,217
From: Philly PA
try holding the pedal to the floor and crank it till it catches.
if it starts then it may have been flooded leaking injectors of fuel dampers or FPR.
It could also also be a the check valve in the fuel pump bleeding off pressure,
try cranking for 6 seconds then stop,
dont touch the gas,
repeat this till it starts,
if this works then its a check valve
Also see if you have an internal fuel pump wires going into the tank where the outlet hose is,
if so then maybe the internal pump has failed
if it starts then it may have been flooded leaking injectors of fuel dampers or FPR.
It could also also be a the check valve in the fuel pump bleeding off pressure,
try cranking for 6 seconds then stop,
dont touch the gas,
repeat this till it starts,
if this works then its a check valve
Also see if you have an internal fuel pump wires going into the tank where the outlet hose is,
if so then maybe the internal pump has failed
Pro
Joined: Feb 2010
Posts: 618
Likes: 1
From: Atlanta GA metro, OTP North
When this happened to my 87 S4 5 speed, it was the CPS sensor plug connection. Loose and intermittent due to crumbling connector. A simple visual/manual inspection will confirm the connector is tight or not.
If your fuel system is OK and the pressure holds after shutdown this may be the issue.
If the fuel pump is original, the check valve on the pump may have failed and not holding pressure. Ether/starting fluid should not be used except in a one time emergency as it can cause detonation. It may also mis-lead you into thinking it is a fuel issue.
Just my opinion, and some things that are easy to check.
I am sure others will have a more rigorous checklist.
Dave
If your fuel system is OK and the pressure holds after shutdown this may be the issue.
If the fuel pump is original, the check valve on the pump may have failed and not holding pressure. Ether/starting fluid should not be used except in a one time emergency as it can cause detonation. It may also mis-lead you into thinking it is a fuel issue.
Just my opinion, and some things that are easy to check.
I am sure others will have a more rigorous checklist.
Dave
Pro
Joined: Feb 2010
Posts: 618
Likes: 1
From: Atlanta GA metro, OTP North
That "should" rule out the pump/check valve, but new parts do fail. Putting a fuel pressure gauge on the right front of the fuel rail should verify the pressure and pressure hold time easily. Any 928 mechanic should do this first anyway.
As my issues have been mostly electrical (connectors) check those out also. Distributor caps/rotors should be checked also, but most ignition issues show up as rough idle or rough running which you don't mention.
Back to CPS connector.
Dave
As my issues have been mostly electrical (connectors) check those out also. Distributor caps/rotors should be checked also, but most ignition issues show up as rough idle or rough running which you don't mention.
Back to CPS connector.
Dave
Thread Starter
Pro
Joined: Jan 2005
Posts: 612
Likes: 0
From: Centennial, WY
I titled this thread "occasionally does not start". It now appears that the correct title should be "does not start". As I noted at the beginning of this thread, the car would occasionally refuse to start unless given a small "zap" of ether. In my latest situation ether did not help and the car sits forlornly in my garage. I tried MrMerlin's recommendation of holding the pedal to the floor until it started - didn't work, just ran the battery down.
This issue is very similar to my situation about three years ago when the "brain" went south and I replaced it and the fuel pump at that time. As you can probably imagine, replacement of the "brain" at $600+ is not where I would prefer to be heading. In this latest issue I have replaced the plugs about a month ago when the initial problem started.
I'm a cheap old bugger and I hate replacing parts on a "guess and go" basis (social security makes you that way) so I've been trying a few cheap things and asking you guys who put a lot of money into your car for opinions. Anybody out there with some ideas of things to try before turning it over to my mechanic?
This issue is very similar to my situation about three years ago when the "brain" went south and I replaced it and the fuel pump at that time. As you can probably imagine, replacement of the "brain" at $600+ is not where I would prefer to be heading. In this latest issue I have replaced the plugs about a month ago when the initial problem started.
I'm a cheap old bugger and I hate replacing parts on a "guess and go" basis (social security makes you that way) so I've been trying a few cheap things and asking you guys who put a lot of money into your car for opinions. Anybody out there with some ideas of things to try before turning it over to my mechanic?
Trending Topics
Rennlist Member
Joined: Jul 2001
Posts: 6,562
Likes: 114
From: New York
As the history and others suggest this is about fuel. Other than holding the accel down you don't report on the other suggestions.
Do you hear the pump? If not, have you jumped the fuel pump relay?
It would help to know if the plugs are wet?
You've been driving it, but is the batt charged, how old?
Do you hear the pump? If not, have you jumped the fuel pump relay?
It would help to know if the plugs are wet?
You've been driving it, but is the batt charged, how old?
Rennlist Stories
The Best Porsche Posts for Porsche Enthusiasts
9 Features and Characteristics That Only Porsche People Understand
Verdad Gallardo
I've Written 500 Rennlist Articles: Here's How Porsche Has Changed Along the Way
Joe Kucinski
10 Most Unnecessary Porsches Ever Built (And Why We Love Them)
Verdad Gallardo
Porsche 911 GT3 S/C vs 718 Spyder RS: 10 Categories, One Winner
Joe Kucinski
This Builder Is Turning Heads With Its Slantnose 911 Creation
Verdad Gallardo
Porsche 911 GT3 Artisan Edition Pays Homage to Japanese Culture
Verdad Gallardo
Porsche Reveals Coupe Variant of the Electric Cayenne With a Fresh Look
Verdad Gallardo
10 Porsche Colors That Have More Personality Than Most People
Verdad Gallardo
Guntherwerks' Final Speedster Creation Is the Ultimate Porsche Restomod
Verdad Gallardo
Team Owner
Joined: May 2004
Posts: 31,233
Likes: 4,217
From: Philly PA
First charge the battery
Pull a plug to see if its wet as Steve suggested but only after trying to start the engine
Then lets go to Relay relay relay.
Also clean the chassis ground and the both battery terminals,
then the fuel pump fuse replace it.
Pull a plug to see if its wet as Steve suggested but only after trying to start the engine
Then lets go to Relay relay relay.
Also clean the chassis ground and the both battery terminals,
then the fuel pump fuse replace it.
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Joined: May 2001
Posts: 14,697
Likes: 598
From: Las Vegas
Pro
Joined: Feb 2010
Posts: 618
Likes: 1
From: Atlanta GA metro, OTP North
1) If the LH brain was rebuilt by one of our vendors and the hybrid chip replaced, it is not likely to be the issue. If it was "replaced" it may have failed again as the hybrid chip will fail.
2) The battery must be fully charged, period. A weak battery will not work.
3) As mentioned, the Crankshaft Position Sensor CPS and it's associated connector can cause all of your symptoms, as it signals the LH "brain" via the EZK the proper timing information from the flywheel.
4) Relays, relays, relays. Fuel pump, EZK, LH numbers 16, 20, 25
Dave
2) The battery must be fully charged, period. A weak battery will not work.
3) As mentioned, the Crankshaft Position Sensor CPS and it's associated connector can cause all of your symptoms, as it signals the LH "brain" via the EZK the proper timing information from the flywheel.
4) Relays, relays, relays. Fuel pump, EZK, LH numbers 16, 20, 25
Dave
Rennlist Member
Joined: Feb 2002
Posts: 7,060
Likes: 42
From: Cambridge England
If it fails to start from a cold start, but starts by adding starter fluid, then the problem may be a faulty Temp 2 sensor or it's wiring.
If the temp 2 sensor goes open or short circuit, then the LH ECU defaults to the mixture setting required when the engine is at normal running temp. Therefore too weak a mixture for a could start.
If the temp 2 sensor goes open or short circuit, then the LH ECU defaults to the mixture setting required when the engine is at normal running temp. Therefore too weak a mixture for a could start.
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Joined: Oct 2001
Posts: 20,506
Likes: 565
From: Bend, Oregon
Lots ofd suggestions already. Don't forget basic no-start troubleshooting. You need spark (at the right time), fuel, and compression. The most common failures are to the electrical system, with spark the most common subset and the easiest to check. A simple clamp-on timing light will let you verify spark at cranking speed. If you have spark but no start, pull a couple of those plugs to see if they are wet immediately after cranking the engine. You might get a fuel odor from the open cylinder too.
What else have you done to the car recently? Serviced the battery? The fuel pump and LH brain get power directly from the battery positive via smaller accessory wires on the positive terminal. Verify that they are clean and tight.
If you didn't replace the fuel pump relay yet, do that now, along with the LH, EZK, FI that are critical to engine operation. Our cars are old and these relays get tired. My FP relay tested OK on the bench, but wouldn't pass enough to build proper fuel pressure. Buy good relays. Roger has them for under $10/ea IIRC, but they come from any of our regular parts suppliers. Cheap local parts store relays don't seem to last long. but may be OK for instant troubleshooting.
What else have you done to the car recently? Serviced the battery? The fuel pump and LH brain get power directly from the battery positive via smaller accessory wires on the positive terminal. Verify that they are clean and tight.
If you didn't replace the fuel pump relay yet, do that now, along with the LH, EZK, FI that are critical to engine operation. Our cars are old and these relays get tired. My FP relay tested OK on the bench, but wouldn't pass enough to build proper fuel pressure. Buy good relays. Roger has them for under $10/ea IIRC, but they come from any of our regular parts suppliers. Cheap local parts store relays don't seem to last long. but may be OK for instant troubleshooting.