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Doug Siegel
 
Join Date: Oct 2007
Location: Bloomington, IN
Posts: 314
little fuel to injectors

In the last 2 weeks I've installed a 1 bar spring, new plug wires, rebuilt ignition distributer, rpm solenoid, and a modified fuel head. When I started'er up it was strong for 3 seconds then stalled. It repeatedly did this 10 or more times. I bled the lines to and from the WUR. Fuel pressure to WUR is proper. Rarly suggested I pull an injector. Rather than pulling the injector itself, I pulled the line that screws onto the injector. When I started the car only a tiny bit of fuel came out. It dribbled like my grandfather's............but even less flow. The car ran for about 3 seconds each time and all together I'd say the fuel from the injector line would cover the bottom of a soda bottle cap. I pulled the fuel head and looked at the pin. It has a latch that does not allow it to fall out. When I pushed it in, it moved smoothly but kinda gets stuck up top before coming back down. I don't really know what to look for here. I do know that fuel is getting through but I don't know how much. There was lots of dribble out of the banjo fittings upon removal. I bought the fuel head from IA.
Help....
Old 04-07-2008, 02:53 PM
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Alan L's Avatar
 
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I would check the flow rates via injectors first. From memory you should expect in the order of 50 cc in 30 sec - at WOT - something like that.
If horribly less, you need to find source. Fuel pumps should be doing about 1100 ccc in 30 secs.
Alan
Old 04-08-2008, 09:41 PM
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Doug Siegel
 
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Alan,
Thanks for the reply, I'll test it out today. What is "WOT"?
Old 04-09-2008, 04:59 AM
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He means Wide Open Throttle- From what I remember- when that pin that your talking about is fully depressed it equals Wide open throttle. Are you sure your not overlooking the pumps like Alan says or possibly the filter? These systems are dependant on big volume...
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Old 04-09-2008, 08:38 AM
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The further you press the air plate down, the more the pin uncovers the metering slots. At max flow rate you should be getting about 50 cc for 30 sec open. This is just an approx number - I just spent about half a day synchronising my injectors - so they are all precisely the same. But this is roughly what they should be doing. If you are starving for fuel, then I would expect something much less than this. Bfore suspecting the fuel head I would suggest verifying the correct amount of fuel is entering the fuel head.
Alan
Old 04-09-2008, 11:14 AM
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Doug Siegel
 
Join Date: Oct 2007
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Got'er running!
I unplugged the CSV and the car didn't start at all. Turns out it was far too lean. I richened it up and she runs. I got the AFR between 14 and 14.5. I figured that a modified fuel head would automatically run rich upon install. Wrong again.

Alan,
How does one synchronize injectors?
Thanks guys!
Old 04-09-2008, 04:13 PM
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I have not got my AFR running yet -(more issues) - but I have read a lot of posts on this - and would offer the suggestion that 14 may be a bit lean - but it depends on your load circumstance, but that is about the leanest number I've seen.
By each fuel line banjo there is a small cap on the fuel head (Allen screw). You need to remover that (rear ones can be tricky - don't loose them (heart in mouth). Then insert Allen key into recess to pick up adjuster - from memory it is the same size as you use for the mixture adjust (3mm). But I think the cap on the fuel head is an odd size - I think I had to get a non- metric to fit.
Depress air plate near WOT, for a time - 15-30 sec. Collect each injectors fuel in a container. Measure. The discrepancies you even out by tweeking the screw in the head. From memory 'undoing' the adjuster reduces flow. Use your noodle -(save a lot of work) - tweek the least number you have to - ie work out whether you want to increase or decrease the fewest number to get the balance point - rather than tweeking them all. If you measure first - you may not have to remove some of the (more tricky ones) caps.
If you have leaned(richened) a couple out, you will end up compensating by richening(leaning) mixture screw.
Alan
Old 04-09-2008, 04:33 PM
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Doug Siegel
 
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Thanks Alan. I had never heard of synchronizing the injectors, but I can see that it might be disastrous to have an injector be way out of whack. Thanks for the info, it's been copied to my personal file.
Old 04-09-2008, 04:45 PM
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It is, in my humble opinion, critical - for best performance, and to prevent melt down with a turbo engine. If you are going to tune the engine for optimum performance using either AFR or CO results, you only get an AVERAGE reading for the 6 cylinders. So a rich cylinder is compensated for by a lean one. But it is the lean one that melts under extreme load (and hesitates etc). So, if you are going to rely on CO or AFR numbers, you need to know that ALL cylinders are the same. Would be preset at factory - but over time injectors deteriorate or get swapped out etc.
You can't tune your car properly unless all the same. Porsche manuals generally mention 10-15% tolerance/variance between worst/best. But if you want the best from the beast you will fiddle till much better (<5%) than that.
Alan
Old 04-09-2008, 04:54 PM
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Doug Siegel
 
Join Date: Oct 2007
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Perhaps I should first remove the injectors and let them soak in techron for a day. I would hope that after blowing some air through them they'd be clear.

Let me see if i've got this straight....
1. remove the 6 allens
2. with engine off and key forward(with green plug on fuel pump unplugged), push sensor plate down for 15-30 seconds.
3. Measure the juice. (how big should the 6 containers be?) Out of the injector or the line that attaches to the injector?
4. Here is where I am confused...Are you saying that there is an adjustment underneath those allens? Accessible only when the allens are removed? If so, do you move in 16ths or bigger?

Thank you. This is fascinating.
Old 04-09-2008, 07:21 PM
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Here is how I do it. Get 6 smallish clean containers - enough to hold 100-200 mls. Need small - bit of a squeeze in places. Unhook your injectors and remove from inlet blocks. Hook injectors back on fuel line. Place container under each injector. (you will pronbaly need to remove some of the induction system - particularly LHS) to get enough room to fiddle. Turn key on. Depress airplate. Injectors will whine/flow.Open plate at least half way to get decent flow. After 15-30sec you will have collected about 50cc in each collector. The time is not critical - just measuring against each other. But need enough to get accurate measure.
Remove cups one by one. Pour into measuring container that can measure to 1 ml.
Record. Say you get from #1 to #6 (These are actual flows I measured a few days ago) 27, 30, 28, 29, 28, 31 cc. You can see 27 (#1) is lowest (leanest) . #6 richest. So you can even them up a lot just by adjusting #1 up and # 6 down. Take the caps of fuel head for #1 and #6. Insert allen key (3 mm I think). Lightly turn/feel for engagement in bottom of hole. Turn about 1/4 turn appropriate way.
Empty fuel jars and start again. The more fuel you collect in a run, the more precise your readings (less error).
After a couple of hours - here si my final run; 65, 64, 64, 63, 65, 64.
The numbers are bigger just because I ran for longer (maybe 30 sec instead of 15).
But it is a variance of 2/64 = about 3%
If I fiddled longer, could do even better.
If 10% variance (+/-5%), at AFR of 12, you have one cylinder at 12.6 If 12.5 is the critical safe point (as many would suggest - hence run at 12), don't be surprised if you melt a piston even tho you were running at your 'safe' AFR of 12.
Regards
Alan
Old 04-09-2008, 08:47 PM
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Doug Siegel
 
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Thanks Alan. I think I got it. I'll post results in a week or less.

What AFR do you suggest at warm idle?
Old 04-10-2008, 04:27 AM
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I'm not the guy to ask about ideal AFr's under various conditions - I'm a bit of a turbo newbie myself - but have had to strip virtually most components off my car just to sort out a heap of issues, and start from scratch. So have read and asked heaps on this board. The idle AFR is not really the critical one - when under load (boost) they have a tendency to lean out - so these seem to be the more critical numbers.
My beast is going on the track so most of it's life will be at WOT or hard on brakes.
But there are a number of very detailed threads on AFR's on this board.
Suggest you search, or ask.
I had to reset my injectors because I pulled my fuel head apart - looking for problems.
Oddly, I have 3 CIS manuals, and none of them detail this proceedure.
While you are in there - check the injector patterns for nice even cones of spray.
If they are not - you need to do something with that injector - clean or replace.
Regards
Alan
Old 04-10-2008, 11:09 AM
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Doug Siegel
 
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I assume that unless one has a machine that tests the injectors' spray, it is difficult to see when still attached to the fuel line. Do most mechanics have such a tester?
Old 04-10-2008, 03:07 PM
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Your CIS system can test the spray pattern - it is doing exactly what it is supposed to do - system pressure wise - when you depress the air plate. You just need to be able to see the injector at work - ie outside the injector block. That is why I use small glass jars to collect my fuel in. Hold the injector up til you can see the tip working.
You should be able to check one or two per calibration run at same time.
Alan
Old 04-10-2008, 05:07 PM
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Doug Siegel
 
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Great. I didn't think the angle the injectors would be upon testing would allow for visual inspection. I was able to get measuring devices from the drug store. The cup measures in increments of 10cc while the syringe is 5cc. Together, with lots of jars and perhaps a funnel, I'll get the job done.
Thanks
Old 04-10-2008, 06:09 PM
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Your injectors will be sitting pretty much as they normally do - just slightly raised on top of the injector blocks. You just need to be able to tweek them up a little to see the tip at work for each one you inspect. The lines are flexible enough to that extent.
Not sure what the syringe is for - I suspect shooting up petrol is bad for your health.
I use a 100 measuring cylinder - graduated in individual mls. You need to be able to read to the ml, or CC - in one shot. You read from the bottom of the meniscus - the surface tension curve on the liquid surface.
Alan
Old 04-10-2008, 09:02 PM
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Macht Schnell
 
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Quote:
Originally Posted by dsiegel360 View Post
Thanks Alan. I think I got it. I'll post results in a week or less.

What AFR do you suggest at warm idle?
Hi Doug,
14-15 is great at idle, if you don't have a stumble coming off idle, and your idle is smooth. You are not going to do anything but keep nice clean spark plugs this way. When I am cruising off boost my AFR runs 14.7. I wouldn't necessarily strive for that at cruise, because you have to work withing the tuneability of your WUR for the whole range, but 14-15 at idle is great for warm idle.
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Old 04-10-2008, 09:49 PM
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Doug Siegel
 
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Quote:
Originally Posted by les_garten View Post
Hi Doug,
14-15 is great at idle, if you don't have a stumble coming off idle, and your idle is smooth. You are not going to do anything but keep nice clean spark plugs this way. When I am cruising off boost my AFR runs 14.7. I wouldn't necessarily strive for that at cruise, because you have to work withing the tuneability of your WUR for the whole range, but 14-15 at idle is great for warm idle.
Thanks Les. Yesterday I was concerned about cruising at 2500-2800-rpm's with a 14.3-14.8 afr.Thought it was too lean. But at 3000-3500 it was 13.8- 14.1. Which is where I should, so do you think there is a problem with 14.3-14.8 at 2500?......Actually, I see what you are saying. There is no adjustment that will change the 2000-3000 range without changing the 3000-3500 range.
Old 04-11-2008, 03:39 AM
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Doug Siegel
 
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Alan,
1.70cc
2. 71
3. 71
4. 70.5
5. 68
6. 70

A couple of the injectors had rust spots at the bigger opening. Replace?

Imagine auto said that the modified fuel head is sent out the door with spot on precision. Hard to tell how well the 20 year old injectors are doing.....on a 39k mile car.
Old 04-11-2008, 01:09 PM
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