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928 dies / won't start when hot

 
Old 07-31-2011, 07:23 PM
  #16  
Maleficio
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The problem after the car warms up sounds like there is some heat expansion going on and causing a loosened ground to open. Car cools off, ground closes again allowing the car to run. As with all gripes, verify all grounds before doing any troubleshooting.
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Old 07-31-2011, 07:28 PM
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Does anyone believe that the basic problem of the car dying when climbing the mountain when it was very hot in Reno (it happened exactly the same way under the same conditions 4 year ago and has started and run fine until now - exact same conditions) was due to vapor lock? AC was not on and I had the heat on full to pull heat from the engine. I have since replaced the fuel pump and check valve. I am trying to figure out if the 2000 rpm and no power/stall that happened 3 weeks after I installed the new fuel pump is a completely unrelated problem.
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Old 07-31-2011, 07:31 PM
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This dude at the bottom of the page found a loosened vacuum hose. He said it fixed his 3000 rpm idle problem.

https://rennlist.com/forums/928-foru...ml#post8756043
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Old 07-31-2011, 07:35 PM
  #19  
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Originally Posted by RBA84 View Post
Does anyone believe that the basic problem of the car dying when climbing the mountain when it was very hot in Reno (it happened exactly the same way under the same conditions 4 year ago and has started and run fine until now - exact same conditions) was due to vapor lock? AC was not on and I had the heat on full to pull heat from the engine. I have since replaced the fuel pump and check valve. I am trying to figure out if the 2000 rpm and no power/stall that happened 3 weeks after I installed the new fuel pump is a completely unrelated problem.

Now that I think about it, when I started having stalling issues, I remember the car idling very high a couple of times. But mainly the car would stall at speed. I found the ground for the L-Jet loose as hell. Barely making contact, and due to heat expansion, the terminal would pull away from contact with the valve cover causing the L-Jet to stop firing the injectors. Having reduced conductivity at the ground for the computer may cause it to process inputs wrongly, and make bad decisions, thus causing all kinds of odd and seemingly unrelated problems.
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Old 07-31-2011, 07:39 PM
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I'll chime in with my usual recommendation, fuel filter.

But 12 years of ownership and only 7 posts here? Wow.
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Old 07-31-2011, 07:42 PM
  #21  
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Without the AC on, the cooler does nothing.

Did you have the heater on because you were worried about overheating or the vapor lock?

Add a fuel pressure gauge to the passengers side fuel rail. The 928 suppliers have them.

Any heat sheilds removed? There are two over each exhaust where they exit from the engine compartment.

Have the fuel lines been replaced? 928srus sells a kit, this is a ticking time bomb if not done, our cars are 24 years old.

These cars are at the age where many of the parts aged due to time, heat and other factors.
Downside is many of these items are not cheap but a majority of the work can be performed by the owner. Most of the jobs have been documented.

I don't think the later cars suffer from vapor lock issues.

Have you done a search on vapor lock?
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Old 07-31-2011, 08:01 PM
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Vapor lock is not something I'm familiar with since I sold the boat with the 350 / holley 750 marine setup.

That is, not been an issue since carbs. Closest we have are broken fuel reg / damper diagphrams that get sucked into the vac collection hoses on their backsides. And significant problems with cars delivered to high altitude markets that also have an auxilliary in-tank fuel pump which either fails outright, else, its hose connectors fail inside the tank, or both. Are there wires leading into the tank for internal pump power on your particular S4?

Sounds like there are a host of problems ripening here.

How about some richer information about your ownership experience and maint records? Maybe some pictures?
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Old 07-31-2011, 08:11 PM
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Dan had a good call on the fuel filter if it hasn't been changed and the car has sat for long periods. Would have been a good time while the pump was replaced. It is a pain, replace the washers on the banjo bolts as they are prone to leak when reused.

87 only has one pump unless optioned. The second would be in the tank if optioned

Do you have a list of the option codes (under the rear floor matt over the fuel tank).
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Old 07-31-2011, 08:38 PM
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Only 1 fuel pump. I changed it. I drive it evey week. It never sits for long. It has been very reliable for the 4 years between the times it died climbing the mountain. I may or may not have fixed this problem with a new fuel pump.

This does not explain the no start that did not involve climbing the mountain - just a warm engine. I never experienced a 2000 rpm idle with the prior failure. As always, once the car returned to cool state it has started and run fine. It cold be weeks or months before the net failure - hence my struggle to figure out what is wrong that causes the car to die. Only common denominator is that it is a hot day.

How do you get the MAF off??? O can't get a scredriver on the clip that holds the rubber hose on - the air intake and fuel rails are in the way. Any simple way to do this???
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Old 07-31-2011, 09:00 PM
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I have rarely posted on the forum. Car has always run great.If I will need to throw serious money into replacing a great many parts I would consider selling it instead. I am the 2nd owner. It is a beautiful ocean metallic blue with a blue leather interior. Great shape - always garaged. Paint still impressive and no cracks in dash, etc. Custom blue sheepskins. Burns no oil, transmission works perfectly - even AC works.

With the exception of the current problem (1st in 4 years) great running. Only 62k verified miles. All receipts, etc. Timing belt and waterpump have 29K miles on them. If this gremlin can be fixed it is a great and great looking vehicle. Two sets of wheels (snow tires on the 2nd set).

If anyone wants to discuss the car, request photos, etc. just let me know.

Dr. Bob
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Old 07-31-2011, 09:07 PM
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Sometimes the clamp bolt orientation requires a surgical approach with 7 mm stubby gear wrench or stubby ratched 1/4 drive 7mm or other creative tools.

Here is a reference that might help in identifying parts beneath the intake and MAF along with relevance.

http://www.dwaynesgarage.norcal928.o...%20Refresh.htm


Outsides of these hold-up well, but at 24 years and 60K miles the engine bays generally need some parts thrown at them to maintain reliability. But most importantly, this fuel line issue is pervasive. Be safe! We've had a young lady owner and a college kid owner that barely escaped devasting fires due to ruptured fuel lines. Sorry coming across dramatic. This is real. And most longterm owners never heard of the situations like fuel line rupture or thrust bearing failure / $90 prevention methods. Not to mention the issues that have most uf us scared of rebuilt water pumps and aware of ground strap problems & collapsed motor mounts.


If you resize pictures to 1000 x 700 or so you can post directly.
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Old 07-31-2011, 09:15 PM
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I still think it is the crank sensor connector to harness - that gives all sorts of weird syptoms.
Did you find the connector yet?
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Old 07-31-2011, 09:21 PM
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I just can't get at the crank sensor connector. Can't even see or feel it. If I can remove the MAF will it be easy to see and clean?
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Old 07-31-2011, 09:23 PM
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How difficult is it to replace the fuel lines on my 97 928? What do the parts cost? Approximately how many hours of my labor?
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Old 07-31-2011, 09:31 PM
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Fuel lines --- about $100. A couple or three hours plus a bit of study.

Last edited by Landseer; 07-31-2011 at 09:52 PM.
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