1.7 keep the fuel injection or get carbs

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volksguy
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1.7 keep the fuel injection or get carbs

Post by volksguy » Thu Mar 06, 2003 5:46 pm

i have a 71 914 1.7L runs well but has its problems its idle seems to never be the same smokes when started and and when cold as it warms the idle goes up so high that it starts to do this wierd rev then cut out thing but if i touch the gas even ever so slightly it dosent do it, it does go away omce well warmed then idles at about 900-1100 once i drive awhile.

so i cant decide to keep working on the FI or ditch it for carbs and if i do what one(s)

upon starting to firgure out these problems i have done a compresion check and have 148 all around so thats seems good then even after 3000-4000 miles my vavles are never more then a thousand or two off only one might be off that much and not always the same one, i was told the motor only had 30-40k on a rebuild but no recipt to prove this i dont know if its true i have noticed some mods to the FI that i wonder might be the culpret to my problems they are as follows the injectors are green ones i belive 2.0L and the thing on the side with the vac hose going to it has been modifed and the pastic was taken out to get the screw in there but maybe that was to tune for the motor mods i know of exhuast maybe it might of euro pistons.

when i got the car a guy at i shop took it for a test drive and said that a 1.7 anit got no power and said i need a 2.0L after driving mine he replied that theres somthing that isnt right about that 1.7

its not fast but gots plenty of pep when you need it. any help would be appreciated

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Mark the canuck
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1.7 keep the fuel injection or get carbs

Post by Mark the canuck » Thu Mar 06, 2003 6:55 pm

Try to keep the FI, carbs on a stock engine kind of suck. The 1.7 has 80hp, so it's not a neck snapper but it should run smooth. Check out this site:
http://members.rennlist.com/pbanders/

If you decide to get rid of the d-jet FI consider my PEFI group buy before you go carbs:
bbs/NonCGI/Forum23/HTML/000668.html

Or you can do the Mega Squirt, it's cheap but you have to build it yourself and wait for the next group buy:
http://www.bgsoflex.com/megasquirt.html

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Piledriver
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1.7 keep the fuel injection or get carbs

Post by Piledriver » Thu Mar 06, 2003 9:03 pm

A worn out motor will make d-jet idle high due to the way the idle circuit is set up.

It will also make it run rich as heck. Or worse;-) It sees low vacuum as a load, and gives more gas.

If the EFI works like that, it is actually telling you "time for a rebuild".

Carbs will not cure that.

Keep the D-Jet. Fix the motor.

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914rrr
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1.7 keep the fuel injection or get carbs

Post by 914rrr » Thu Mar 06, 2003 9:12 pm

Keep the d-jet. This site http://www.914fan.net/djet.html
does an excellent job of explaining & troubleshooting d-jet injection. Another good explanation of fuel injection can be found in the "complete idiot's guide to VW's" book.
I've owned 16 914's and the ones with carb(s) were never as fast as the injected ones.
Also, the carbed ones always got lousy gas mileage. Whatever you do, don't get the single 2bbl Holley-Weber, they are horrible!

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Bleyseng
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1.7 keep the fuel injection or get carbs

Post by Bleyseng » Thu Mar 06, 2003 9:18 pm

148 is a excellent reading so I would also try a vacuum gauge to see what it reads. 15hg steady at warm idle??
The green injectors? rebuilt soon time ago? Could be it has the 96mm P& C's in it so they swaped to the 2.0l injectors. What is the code on the MPS? What CHT is installed? I would fix the FI as carbs on a stock motor have less hp and run crappy due to the FI cam.
Geoff

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76 914 2.1L
www.914Club.com member

volksguy
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1.7 keep the fuel injection or get carbs

Post by volksguy » Thu Mar 06, 2003 10:42 pm

i am not sure what mods are made but soon need to pull the motor and trans to put in my new trans also want to go through and put in new seals on the pushrod tubes so i will be able to check out the pistons.

i have had a vac gauge on it and it was about 15-18 and steady it is running rich i would say quite rich i get about 22-24 mpg on the highway and have been told it should be like 30-32 i do not have a way to check fuel presure but was wondering if the green injectors are the cuase of the rich running and poor gas mileage.

if i could find injectors at the juckyard what ones should i get

volksguy
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1.7 keep the fuel injection or get carbs

Post by volksguy » Thu Mar 06, 2003 10:48 pm

where is the code on the MPS? and where is that. i think you mean that thing that i sayed is where the vac hose goes to it and its on the side of the engine compartment and what is the CHT and where is it at and what should i look for about it.

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Dave_Darling
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1.7 keep the fuel injection or get carbs

Post by Dave_Darling » Thu Mar 06, 2003 11:43 pm

First, you don't have to pull the heads to change the pushrod tube seals. This is a vast improvement over the Type I. You can even do the job without removing the engine.

Second, just about all the D-jet info that exists on this planet can be found at http://members.rennlist.com/pbanders .

Third, the MPS has a part number on the side. Look around it, you should be able to find it. The MPS should be over on the right side of the engine bay; it has a single hose and a four-wire wiring bundle plugged into it. The hose should plug into the manifold. There are hose diagrams available on the Pelican Parts website (see my sig below for the URL). You may have to do a bit of extrapolating, as the 1.7 diagram we have is for a very early car and the later ones have some extra "bits".

Finally, the CHT is the Cylinder Head Temperature sensor. It should be located in the right-side head, near the #3 spark plug. Look for a single (thin) wire going through a hole in the engine tin over near the #3 plug.

--DD

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1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

volksguy
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1.7 keep the fuel injection or get carbs

Post by volksguy » Thu Mar 06, 2003 11:58 pm

what should i check for on the head temp sensor i know the one your taking about do i need to take a reading from it with a volt meter and measure the ohms if so how do you make a volt meter do this i got a older one that is a analog type i know how to read volts but not ohms also i belive you need to zero the ohms reading how do you do this

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Bleyseng
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1.7 keep the fuel injection or get carbs

Post by Bleyseng » Fri Mar 07, 2003 11:07 am

Well sounds like the MPS has been adjusted Image which is bad so follow the link above to Kjell article at Dgi.net to adjust the partload so it runs right. Try not to move the outer screw as that adjusts the WOT.
To check the CHT you will need a Ohm meter or just buy a new CHT as they a cheap. My bet is the car has the 96's in it thats why the PO installed the 2.0l green injectors. The orginal 90mm P&C's were domed high compression ones so if you do pop off a head look and measure them.
Also, go to http://members.rennlist.com.pbanders and read the djet articles so you understand how it works and how to troubleshoot it your self. This is the bible of djet FI. If you have any questions Brad will also reply to you.
Geoff

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76 914 2.1L
www.914Club.com member

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Dave_Darling
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1.7 keep the fuel injection or get carbs

Post by Dave_Darling » Fri Mar 07, 2003 1:06 pm

Many, but not all, voltmeters have ohmmeter settings. If yours doesn't, then you need another meter. Frankly, the $20 Radio Shack multimeters (Volts/Ohms/Amps) work quite well enough for most automotive use.

Set the meter to "ohms", connect the leads to "COM" (or "GROUND") and "V/Ω", and set the range (if it isn't auto-ranging) to 2K or 20K ohms. Unplug the CHT sensor from the wiring harness (there's a long skinny box connector, the wire from the CHT pulls out of that connector) and put one test lead onto the metal connector on the end of the CHT wire. Touch the other lead to the head, or to another good ground.

The sensor should read between 1500 and 3000 ohms when cold, depending on the exact sensor and the exact temperature. When warm, the sensor should read less than 300 ohms--and usually less than 100. That's when the engine is all the way warmed up.

Both the Kjell Nelin article and Brad Anders' website have a lot of info. I think the Nelin article is a little easier to digest, but Anders' site is more complete.

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

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raygreenwood
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1.7 keep the fuel injection or get carbs

Post by raygreenwood » Fri Mar 07, 2003 6:01 pm

Yep...keep the injection. It sounds like vacume leak issues, but could just be tuning. By the way, if they have removed the screw in plug under the epoxy on the MPS (that thingy they took the plastic out of)...yes they had to remove the plastic to get to the mixture adjustment screw. But...the cover scrw itself isthe oute rstop adjustment. If it is missing or screwed in or out too far...it will cause this very problem. Check your auxiliary air regulator as well. Check for all vacume leaks...check the resistance of the injectors. Clean your trigger points...and as Bleyseng mentioned, do a basic reistance test with a good ohmeter on all of your sensors while its cold...them hot. It may simply be an adjustment. Ray

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raygreenwood
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1.7 keep the fuel injection or get carbs

Post by raygreenwood » Fri Mar 07, 2003 9:26 pm

A further note...the aluminum plug in the back of the MPS...for a baseline adjustment, at idle,....meaning, when the copper diaphram that holds the adjustment screw in the middle is vacumed in (rev the motor with the aluminum plug out..and you will see this copper plate move in and out...to know what I mean)....when re-installing the outer aluminum cover plug, clean the threads very carefully so it turns very easily, and turn it in unjtil it just contacts the plate. DO NOT DO THIS WITH THE ENGINE OFF!If you actually go too far, the car will stall. Once it contacts the plate, turn it out 1/2 turn. Thats a good starting place. If you are out over about 1.25 total turns...you will get a hideous rich spot upon acceleration of the line, and through the range anytime the throttle is opened more than about a 1/4".
If it pops from the exhaust or intake manifold when pulling of the line, or clatters..or acts lean in any way...increase the amount you turn this screw outward no more than 1/8 turn at a time.

This simple looking aluminum screw is the outer stop for the copper diaphram plate. The purpose of that plate is to flex outward when atmospheric pressure floods into the chamber when opening the throttle plate. It has two functions (1) since the barometric chambers inside the MPS are smoooshed down to a narrower size when the vacume is released..they allow the armature to move outward from inside the coils. The distance it moves..and the rate of speed at which are moves are both equally important to acceleration enrichment. The outward flex of the copper plate removes spring load on the armature at a quicker rate than the movement of the barometric chambers. Its like an accelerator pump. (2) The copper plate is more sensitive than the barometric chambers to part throttle vacume changes. Its flexing is able to make more encremental movements in the midrange, than the barometric chambers. Its function at this stage is as a corrective device. So...make sure of where that simple looking aluminum cover plug is set at. Ray

volksguy
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1.7 keep the fuel injection or get carbs

Post by volksguy » Sat Mar 08, 2003 12:14 am

how can i post pics want to show the mps and the mods to it

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raygreenwood
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1.7 keep the fuel injection or get carbs

Post by raygreenwood » Sat Mar 08, 2003 1:48 am

It would be easier just to describe them. Other than removing the epoxy sealer from the back screw in plug...there really should be very little (visually ) for us to see. Ray

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