need help - engine 2.0L

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knabini
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need help - engine 2.0L

Post by knabini » Mon Jul 15, 2002 12:24 am

Hi all. After putting the engine back (clutch job) it works this way: cold start is ok, but idles a bit fast 2000rpm, after warm-up drops to just under 1000rpm (sometimes needs help by pressing gas).
when hot it starts and dies in a second, unless I press gas to keep in going in between 1500-2000rpm for a sec or two. then it keeps spinning at 2000rpm. One more thing - engine drops revs very slow (1000 rpm drop takes two seconds or even tree!!!). is it vaccum? does throtle position switch need adjustment (never done that)? or something else? 1973 2.0L
thanks all.

------------------
"why to live, if there'z no PORSCHE?"

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Dave_Darling
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need help - engine 2.0L

Post by Dave_Darling » Mon Jul 15, 2002 3:55 pm

cold start is ok, but idles a bit fast 2000rpm, after warm-up drops to just under 1000rpm (sometimes needs help by pressing gas).

Normal warm idle should be about 850-900 RPM. So that sounds normal, except for the part about needing to help by pressing the gas.


when hot it starts and dies in a second, unless I press gas to keep in going in between 1500-2000rpm for a sec or two. then it keeps spinning at 2000rpm.

I hear some 2.0s even used to do this when new. You might try building up fuel pressure by turning the key from "off" to "on", letting the fuel pump do its 1.5 second "buzz", then turning back to "off" again. Try 3-4 times, then start the car. This sometimes works, sometimes not.


One more thing - engine drops revs very slow (1000 rpm drop takes two seconds or even tree!!!). is it vaccum? does throtle position switch need adjustment (never done that)?

Vacuum. Maybe over-advanced timing, but more likely vacuum. If the Decel Valve is stuck open, for instance, or you have the advance and retard hoses on the distributor switched around, you can get this. Or if you have vac leaks elsewhere.

--DD

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

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

knabini
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need help - engine 2.0L

Post by knabini » Mon Jul 15, 2002 10:34 pm

Decel valve? I don't even know where it is located. Nor now to test it. The hoses to vacuum advance are placed according the diagram on pelican's site (When I bought 914, they were diconnected. PO didn't even think what those hoses might be doing there). The thing I worry about is the elbow with two inlets, plugged into the throttle body (one connects with oil filler housing, another - with something else that looks like the pressure regulator, but without the adj. screw, which sits beside the battery; there's one more hose comes out from it and attaches to air filter housing). I can't find a replacement anywhere (is it avail. thru Pelican?). I'll try "pumping" the fuel on hot engine, as you suggested - let's see if it helps...
fyi the fuel pressure is at 30 psi.
off topic - there's a relay board in eng. compartment (left front) which has a relay or two, bunch of plugged wires and two slots for the fuses. What are those fuses for and what ratings (8 amp, 25 amp)?
Thanks, Dave.

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Racer Chris
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need help - engine 2.0L

Post by Racer Chris » Tue Jul 16, 2002 7:29 am

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by knabini:
<B>Decel valve?
...another - with something else that looks like the pressure regulator, but without the adj. screw, which sits beside the battery;

What are those fuses for and what ratings (8 amp, 25 amp)?
</B><HR></BLOCKQUOTE>

That device is the decel valve.

front fuse, 8A - heater fan;rear fuse, 25A - fuel pump



------------------
Chris F.

www.tangerineracing.com

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Dave_Darling
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need help - engine 2.0L

Post by Dave_Darling » Tue Jul 16, 2002 4:53 pm

Relay board diagram:
http://www.pelicanparts.com/914/parts/E ... ic_73E.jpg

The front relay is optional, and was used for the rear window defogger. The rear one is used for the heater blower motor. The two in the middle were used to send power to the D-jet ECU, and by the D-jet ECU to power the fuel pump. (L-jet cars have those functions taken over by the "dual relay", so they usually only have one or two relays installed on the board.)

The wires going to the board varied a bit in color and destination over the years, but the actual traces in the board (and the whole of the board itself) were unchanged through the years. You can see the traces on the above image if you look closely.

--DD

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

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

ray greenwood
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need help - engine 2.0L

Post by ray greenwood » Tue Jul 16, 2002 5:59 pm

This is a common problem. Its running rich. The reason its running rich will either be a vacume leak...very possibly in the MPS. A small crack in the copper plate can cause thisvery symptom. Also...if the MpS for any reason is grossly out of adjustment. Another good cause is a leaking fuiel pressure regulator (bleeds down)...and or a weak fuel pump. Ray

knabini
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need help - engine 2.0L

Post by knabini » Wed Jul 17, 2002 12:47 am

ok...thanks guys for info...
How can I test the Decel. Valve
MPS
and press. regulator?
Dave, turning on and off ignition 3-4 times (to prevent eng. to stall) didn't work.
With all this "problems" I have another one: after a few minutes of driving, it idles at 2000 rpm. I tried to lower revs, but eng. comes back to 2000 shortly.

ray greenwood
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need help - engine 2.0L

Post by ray greenwood » Wed Jul 17, 2002 6:56 am

If the engine is idleing that high....you have a vacume leak pure and simple. You gotta have air in the injection system to idle that high. If you have air...the MPS will add the fuel. Going from memory I cannot remeber if the 2.0 has a breather tower exactly like the 1.7. That is...with the "funnel" and the 12mm hose leading to the center intake plenum. If it does....the nipple that the hose connects to....if its vertical...and plastic with a round, plastic, slotted nut holding it in (kind of like a bulkhead fitting)...that is your PCV valve. It is accessable by a "D" shaped plug from underneath. They always fail...and can pass enough air to do what you describe. The deceleration valve can also pass enough air to do what you describe. It will have a hose coming fome some where in the air cleanert system...running through the valve and leading to the center plenum. It also has a small 3-4mm vacume line. Pinch either one of the larger hoses with a pair of pliers. If it stops the idle problem...thats it. The MPS can be tested for vacume with the car off simply by disconnecting the hose and applying vacume to see if it hold vacume. Any leakage no matter how small is not allowed. If the intake runner boots and the TB seal have not been replaced...they are suspect. Injector seals are suspect too...but usually they cannot pass enough air for 2000 rpm. A bad auxiliary air reg can do this to. Remove the air cleaner side of the aux. air reg hose when its warmed up. It should have no vacume/air passing through it after 8 mins of running. The small weird boot (if you have it) between the aux. air regulator and the center plenum....with the vacume line running to the decel. valve is also suspect. It may look good...but is usually cracked. Let us know what you find. Ray

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Dave_Darling
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need help - engine 2.0L

Post by Dave_Darling » Wed Jul 17, 2002 7:48 am

The other possible cause of a high idle is overly-advanced timing.

For a good concise article on D-jet EFI, see http://www.914fan.net/djet.html .
For even more info about D-jet, see http://members.rennlist.com/pbanders

--DD

knabini
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need help - engine 2.0L

Post by knabini » Wed Jul 17, 2002 11:37 pm

Thanks, Ray and Dave. I'll probably do these tests over the weekend; have plenty of time to read that site about FI you gave me. I'll keep you posted. George...

[This message has been edited by knabini (edited 07-18-2002).]

knabini
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need help - engine 2.0L

Post by knabini » Sat Jul 20, 2002 8:31 pm

Pressure sensor is found to be leaky. When I'll get the replacement, I'll continue with the rest of tests. Are pressure sensors repairable/rebuildable? Or are they available rebuilt?

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Dave_Darling
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need help - engine 2.0L

Post by Dave_Darling » Sun Jul 21, 2002 9:34 am

Rebuilds are available. They do not respond the same way as the real thing, as some of the internal parts that are used in the rebuilds are of different materials than the original.

They're better than nothing, though!

--DD

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

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

knabini
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need help - engine 2.0L

Post by knabini » Sun Jul 21, 2002 12:22 pm

Does anyone know where I can buy the rebuilt one? I've seen one on E-Bay (rebuilt) $145.00. What's your opinion : is it worth the money?

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Bleyseng
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need help - engine 2.0L

Post by Bleyseng » Sun Jul 21, 2002 10:58 pm

Take it apart per Brad Anders webpage at members.rennlist.com/pbanders
Inspect the diaphram for cracks without changing the inner or outer screw!
If all looks good reseal the side that has the paper gasket with a light even coating of gasket sealer. Then reassemble and test, it should be fine.
Geoff

knabini
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need help - engine 2.0L

Post by knabini » Mon Jul 22, 2002 11:54 pm

Just a thought...if the diaphram is broken, can we use some diaphrams used in the mechanical fuel pumps (used for carbs) as a replacement (off course they must have the same outer diameter (or larger)? Again, it's just a thought...

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