Drivability problem solved with new injectors - Page 3

Bobboloo · Bobboloo's Garage

Quote:

Originally Posted by rpmoore2

Hi all,

I have a 81 3.0L in a 77 911S.

Just recently I had a drivability problem where between start up to 2300 RPM under load the car would sound like it was running on half the cylinders, stumble, hesitate and hiccup. Oddly it would clear up on full throttle after around 2300. The car was fine up to the problem a week ago and oddly it started acting up right after putting gas in the car.

So I took it into the shop and the response was I need new Fuel Injectors. One was totally clogged and the others were border line. So we decided to replace all of them.

Anyway I picked up the car that night and well the same problem was still there. So I left the car at the shop and told them to look at it again. Anyway they confirmed that I was right about the stumbling and a little surprised.

So they checked the injectors and 2 were clogged (worst than before). This time they cleaned out the lines, flushed the system and replaced the 2 again.
The shop wasn't sure if it was fuel or just bad injectors. They also adjusted the cold side of the WUR for me to help with the cold start.

"The car was fine up to the problem a week ago and oddly it started acting up right after putting gas in the car."

This statement to me is a smoking gun. Especially when you consider that the new injectors got clogged. When you say they flushed the system does that mean they cleaned out the gas tank? If they didn't then why would one think the problem would go away by working on everything downstream?

If the gas tank has rust it will need more than rinsing out. It will need to be restored.

Jim Williams · 09-10-2008, 04:52 AM

Quote:

Originally Posted by rpmoore2

..............

If someone could clarify the fuel pump relay and how it works. When the airflow sensor is closed is there ground and hence the fuel pump doesn't work, and then when the contact is broken the ground is broken, and a solenoid in the relay connects the power to the fuel pump. Or is it the reverse.

Thanks

Have you read the description on my website of how the fuel pump relay works? Look under CIS Components > fuel pump relay.
http://members.rennlist.com/jimwms/CIS/CIShome.html
There is a lot of information there that could maybe answer some of the questions you are having. What the site can't do is figure out problems resulting from someone modifying the wiring from the factory diagrams.

This is for the '77, but the wiring is basically the same. It should fit with the website description in how it works. Current track 106 (in the yellow at the bottom of the picture) is the fuel pump. 105 is the safety switch.

rpmoore2 · 09-10-2008, 04:43 PM

Point very much taken on the gas tank. When I got the car back from the shop all they said is the system was flushed. They weren't specific. He wasn't sure if the 2 of the new injectors were just bad or the fuel system recreated the problem so they flushed the system as a precaution. I forgot to ask if they did it from the fuel tank. The car was pretty empty when I picked up the car. Regardless I can say I have driven the car for a week now and things are better. I definitely will pose this question about the tank.

Jim, thank you for all your help with the latest and prior. I am still having problems locating all the parts. Funny though some one is selling a Euro 3.0l motor in the parts mb and they had pictures at all angles. I think I see the AAV behind the AFS.

Regardless I called another shop who is really known in the Milwaukee area and I want them to document the parts I haven't found, evaluate the euro conversion the best they can and install my pop off valve. They said they have a book on Euro conversions. I asked them too to test some of the wiring for the fuel pump relay which I am beginning to wonder is bad. I take the car in this Saturday. I will have the facts next week.

Regardless I will study the diagram you gave me tonight very carefully. Thank you so much. I really appreciate you responding. I kept the service book too.

rpmoore2 · 09-10-2008, 07:00 PM

New information . For the most part I believe in the fuse box -the amount of tampering seems minimal. When I take it in on Saturday I will confirm this.

Jim your documentation:
“Operation of the '76 and later relay:

The relay has two sets of contacts - Normally Open (NO) and Normally Closed (NC). In electrical lingo, "Normal" infers no power on the relay coil. On the basic Porsche round relay, pin 87 is NO, pin 87a is NC and pin 30 is the "arm" of the contact that switches between the two.”

My car:
Not only is the fuse box jumped someone tampered with the Fuel Pump Relay as well. I can post pictures tomorrow.
Facts.
a. Connector on 86 and 87 on the fuel pump relay were shaved off. Don't know why. See the damage of someone doing this.
b. A jump wire from a blower fuse/rear heated window is connected to the fuel pump on the fuse panel. The fuse panel cover proves those connections.
According to your description, terminal 87 is NO. Mine is shaved off. So in order for the relay to work some one jumped blower motor fuse connection to the fuel pump connection on the fuse panel. That makes 30 NO (I think) all the time and in turn makes 87a open and turns on fuel pump. I think when the ignition is on Blower Motor/heated rear window is only active with ignition on so they were creative.

So am I correct based on your description? Does my theory seem reasonable based on how I describe it.

If so why would they make the fuel pump work all the time. Maybe this is a good sign that the wiring for the euro afs contact switch maybe wired correctly.
One of my points yesterday I asked if the Fuel Accumulator or Check Valve was bad and someone would not fix that. I think this is premature to ask this until I prove the the afs contact however is this possible.

Thanks Jim for the wiring and your web site. I am finding it very helpful. My book has been a good resource too.

rpmoore2 · 09-10-2008, 07:19 PM

Another piece of evidence I forgot mentioning. As I said before when I pull the fuse on the jumped wire the pump stops working. However, when I pull the relay the pump stops working as well.

So given my fuel pump relay is definitely bad/physically damaged can I just order one and install it. What damage would I do. Or should I really verify the electrical wiring first.

Again I don't see any other tampering other than the jumped wire and the fuel pump relay damage.

One thing the shop said today, who did the rebuild, is that when they take out the motor they just disconnect the wiring harness. And I would assume they just take off the entire fuel system in whole of the engine case. So he doesn't think any wiring would be mixed up. He wasn't sure about the original conversion.

Regardless I realize I need to test terminal 85 in the fuel pump relay and that should prove the other wiring for sure.

rpmoore2 · 09-10-2008, 07:33 PM

Jim I still have lots of reading. I am going through your fpr description and having trouble . It will take a couple of attempts to read through it. Also still working on your wiring diagram. Thanks

rpmoore2 · 09-10-2008, 07:35 PM

One thing that I noticed in your web site. The FP is protected from a different fuse.
"(Note that you can't jumper power to the fuel pump by jumpering +12 Volts to a fuse on the fuse panel. The fuse which protects the fuel pump is in the wiring that goes from the NC contact to the ignition switch)."
Am I exposed with the PO tampering. Thanks

rpmoore2 · 09-11-2008, 06:48 PM

Just for anyone who wants to see my fuel pump hot wired here you go. I did not do this.

Notice the file marks on the fuel pump relay edge where terminals 86 and 87 are shaved off.

I would be interested in knowing if anyone has ever seen this setup before.

rpmoore2 · 09-12-2008, 09:38 PM

From http://members.rennlist.com/jimwms/CIS/CIShome.html
"The fuse which protects the fuel pump is in the wiring that goes from the NC contact to the ignition switch)"

Where is this fuse located in the car?

rpmoore2 · 09-12-2008, 09:46 PM

Per http://members.rennlist.com/jimwms/CIS/CIShome.html and the components desc of FPR.

I've read the description of the FPR, followed by the wiring diagram and normally closed relays and I cannot understand why you would need to cut terminal 87 on the relay. If I understand it correctly, wouldn't the relay be normally closed (de-energized) all the time by cutting terminal 86. So cutting 87 would not serve any purpose.

Just curious.

rpmoore2 · 09-12-2008, 09:51 PM

First off is the wiring to terminal 87a on the FPR - from the ignition (when on), to a fuse to a post on the fuse panel and finally to 87a.
If this is correct, then by jumping that post on the fuse panel would create a short circuit. If so, I am wondering if this fuse is blown.

Jim Williams · 09-13-2008, 04:38 AM

Quote:

Where is this fuse located in the car?

On the fuse panel in the trunk. Read below about my somewhat confusing statements about jumpering power to the fuel pump.

Quote:

I've read the description of the FPR, followed by the wiring diagram and normally closed relays and I cannot understand why you would need to cut terminal 87 on the relay. If I understand it correctly, wouldn't the relay be normally closed (de-energized) all the time by cutting terminal 86. So cutting 87 would not serve any purpose.

I agree. If the fuel pump relay circuit is working as it should, there would be no purpose served in cutting any pins off the relay.

Quote:

First off is the wiring to terminal 87a on the FPR - from the ignition (when on), to a fuse to a post on the fuse panel and finally to 87a.
If this is correct, then by jumping that post on the fuse panel would create a short circuit. If so, I am wondering if this fuse is blown.

You should be able to tell if the fuse is blown. I'm not clear what you mean by jumping the post. If you mean jumping the fuse, that is, placing a jumper wire across the fuse terminals, then this obviously defeats the purpose of the fuse. My description of jumpering the relay to get the fuel pump to run is admittedly somewhat confusing, but since I now have no access to my website, I can't change it until someone on the server end fixes the problem.

The photo shown of your fuse panel indicates to me you have a broken fuse post in the position for the power windows, and someone added a fuse for this function. If I am correct, this would have nothing to do with the fuel pump operation.

I don't believe anyone is going to be able to determine why someone modified your fuel pump wiring before you came to own the car. If nothing else besides the relay has been butchered, the relay will never energize as designed, and the fuel pump will run when the ignition is switched on, and during startup. If there were no other mods to this circuit than the relay, then a new relay should put things back like they were.

rpmoore2 · 09-13-2008, 06:14 AM

Then the broken post you refer to is the fuel pump fuse according to the plastic cover. See my photo below.

My car does not have a fuse for the power window. I know this because on my first test I pulled the fuse on the jumped wire and the pump stop working.

You can't really make out the words on the cover other than it is the fuel pump.

I wonder what happen to the fuel pump fuse and the wire from the ignition.

rpmoore2 · 09-13-2008, 07:02 AM

From the ignition to the fuse for the fuel pump according to my wiring. If #11 on parts diagram broke off then what happen to the wire. What color is it? All I can see from the schematics is that it is red. I can see one doubled up on fuse 5. And I cannot see any spare wires just hanging.

I bet you someone tried to replace the fuse on the fuel pump and broke it. Then wired off my air blower to the fuel pump remaining post. That powered the relay. Of course I will never know.

Funny thing is it is a $20 part. And just 3 wires to hook up.

Jim Williams · 09-13-2008, 09:12 AM

Your fuse panel cover does not agree with any information I have about the location of the fuel pump fuse. Also, page 0.1- 3/23a of the factory manual says - " The electric connection for the window regulating motor is no longer made at fuse S16, but S21 instead".

No 911 of this era, '76 - '83, that I'm familiar with, has had the fuel pump fuse in the #21 fuse location. The '77 factory wiring diagram says fuse #16 is the fuel pump fuse. That's counting fuse positions from the front of the car. A plastic fuse cover I have in my parts box agrees with this. Several of the diagrams of the later (than '77) cars of this era (SCs) also agree with this. The fuse #16 in your photo has no apparent connection here.

My recommendation is that you turn this problem over to someone who is familiar with the wiring on these Porsches, knows how to troubleshoot electrical circuits, has the factory diagrams, and has the car in front of them.

boyt911sc · boyt911sc's Garage

RP,

At this point, the disapointment you are having with your car/shop is not really that bad. The situation you are now could be remedied by correcting the wiring anomally. If you're just a couple of hundred miles away from me, I would offer to take a look at this problem. However, if you like to get involve in fixing this problem, we could communicate via email, pictures, and over the phone.

Your wiring problem with regards to your FP relay is not difficult to correct otherwise, I would have stayed away from your post. But after following the progress of this thread for several days, I felt a fellow 911 enthusiast needs some assistance.

BTW, I'm not a CIS expert like Mr. Williams but I find CIS troubleshooting easy and fun. PM sent too. Good luck.

Tony

Jim Williams · 09-13-2008, 01:54 PM

RP,

Here's another bit of data for you: I went back and checked the wiring diagram in the factory manual for the '76 911 and it shows the fuel pump fuse to be #21, the number of the fuse position where you have the add-on fuse in the black wire. Maybe the factory forgot to do the update on your '77 to fuse #16. The '76 diagram shows that the broken terminal in your photo got it's power from the top terminal at fuse #12 which was for the fresh air fan. Hope this sheds some more light on your problem. (Does the VIN on your car verify that it's a '77? Just curious.)

Tony,

Thanks for the compliment. Now I'll know who to contact to share the next fun CIS issue with.

rpmoore2 · 09-13-2008, 05:12 PM

1977 for sure.

Per http://www.adelgigs.com/911vin%20numbers.shtml
1977 (J Series)
911 S Targa US 911 721 0001 TO 911 721 2747

My VIN# is *9117210064* - according to the door label build date is 07/76. I looked at that 7 twice to be absolutely sure.

How about that

:-is this the 64th car off the assembly line for the US market?

rpmoore2 · 09-13-2008, 05:37 PM

Quote:

My recommendation is that you turn this problem over to someone who is familiar with the wiring on these Porsches, knows how to troubleshoot electrical circuits, has the factory diagrams, and has the car in front of them.

I plan to this Monday. This FP safety switch or lack of bugs me.

This latest information that I have an early build 77 with a 76 wiring and a broken fuse box is very valuable information to pass along to the shop. It will save them time.

Hopefully I can get the remaining CIS part #s too.

Jim Williams · 11:20 AM

Quote:

My VIN# is *9117210064* - according to the door label build date is 07/76. I looked at that 7 twice to be absolutely sure.

Here is a little more confusion to throw into the ring.

Porsche's build dates for a model year are August of the previous calendar year through July of the following calendar year (that is, July of the car's model year).

The I-series (model year '76) production was 8/75 - 7/76. The J-series (model year '77) production was 8/76 - 7/77. You might deduce from this that your car was possibly a leftover from the '76 model year run, labeled as a '77. ???