'73 1.8l vapor lock fix? EFI hot-start no-start

[MarkRobinson]

My newly acquired 914, still fuel injected, starts quickly when cold, but consistently will not catch when starting (excess fuel it smells like) until it's cooled down 15-20m minimum.

Any thoughts?

[Tobra]

Maybe vapor lock, will it spin and not fire or does it not spin?

Could be air leak cuasing lean condition too. It is air flow controlled, and if unmetered air is getting in there, it will make it run kinda hot. Does it run okay when warm then won't start or does it start running hot and crappy when you drive it?

[MarkRobinson]

It starts & runs decently enough, but if you stop the engine when hot, it needs to cool down before it will start back up. Otherwise, it just whirs & whirs with some light catching, & some fuel smell.

Thanks, Mark

[Dave at Pelican Parts]

Vapor lock would give you too little fuel, not too much.

What's the fuel pressure when it doesn't want to start? Zero or very little pressure would indicate vapor lock.

Which engine and fuel system do you have? The 1.8 wasn't available until the 74 model year, though it's easy to swap motors. The D-jetronic of the 73 1.7 would have a round air cleaner, while the L-jetronic of the 74-75 1.8 would have a square one over at the left side of the engine bay.

--DD

[MarkRobinson]

It's a d-jetronic (round cleaner) 1.7l. I just (last sat) got the car, & haven't had time to fiddle with it, so dunno the fuel pressure. Can you tell me what it should be both with/without vacuum? Smells kinda rich when idling, but hard to start/no-start when it's warm.

I think I wanna get it running good enough for now while I investigate my engine options: enlarge this one, or ditch for an EFI 2.0.

Thanks Dave...ordering a few things for the car on Monday from you..doing my homework on what I need this weekend.

[Dave at Pelican Parts]

There should be no vacuum connection to the fuel pressure regulator. There should be a fuel line into, and a fuel line out of. Spec pressure is 29 PSI any time the pump is running.

It may be running too rich. Does turning the adjustment on the "brain" have any effect? CW is rich, CCW is lean. Count the number of "clicks" you turn it so you can get it back to where you started!

Does it have a resistor plugged in between the head temp sensor and the EFI wiring harness? The CHT sensor is over by spark plug #3; the wire comes out of a hole there and plugs into a boxy plastic connector. If there's a resistor in that circuit, remove it and see how that works.

--DD

[MarkRobinson]

Ok I'll look at that resistor tonight.

Last night I replaced the spark plugs gapped at .024 (3 normal, 1 kinda lean), cap, rotor, points, & condensor, with the point's regapped at the contacts @ .016, then did my best to time the motor at 27d (I think I saw a triangle in the fan with the timing light, with both vacuum lines disconnected at the distributor @ 3500rpm, setting it to 27d.

Runs quite a bit smoother, though smells richer at idle that it did before. I'll check my plugs tonight to see if there's any changes since last night.

I guess the only thing I really need to check is that fuel pressure changes with vacuum, since the D-Jetronic developers were so nice to put fuel pressure adjustment measures into their systems unlike 99% of most EFI systems out there.

[MarkRobinson]

Ok, my hot-start issue still remains: dont' see the before-mentioned resistor either.

-73 914 D-Jet 1.7l. runs good, but not consistant & has the following issues after my tune-up (Tune up consists of new plugs gapped at .024 (#4 looks leaner than the others), New cap, rotor, condensor, points set at .016), & timing re-set at 27d at 3500 w/o vacuum lines on the distributor. I also verified both vacuum line sources & all breathers & such). It has fresh wires, & a fresh oil change of Mobil 1 20-50.

Two major problems: 1, After the tune up, I lowered the idle to about 1050 or so (it was at about 1600) via the throttle set screw, but at that level, about 1/2 the time, the idle will slowly drop until the car dies. the Idle will also sometimes increase itself as it's low...very strange. When the idle is very very low, I have to tap the throttle a few times to get it to come up, otherwise it usuallly dies once I start pressing the throttle with it that low.

Second & more troublesome issue: once it dies when hot, it doesn't want to re-catch when the starter's whirling it. If I floor it while I start it, it will start (figured this out last night sitting in a parking lot, waiting for it to cool down so it would start). When I got the car, & this still holds true, if it cools down for about 10-15m, it will start back up.

I even got keyed on Sunday for leaving it under the Home Depot awning while it was cooling (& raining) so I could re-start it.

So, with my readings, the only thing I can think of is the air temp sensor (replace) & the AAR valve (check for function). Any other thoughts??

Mark

[MarkRobinson]

Oh, if these are speed-density, where's the MAP sensor to this EFI system? I don't recall reading about it in my Haynes.

Mark

[Nostril Cheese]

1.7L's dont have a MAP sensor like regular F.I. systems.

They have a vacuum sensor that bolts to the passenger side of the engine tray. It looks like a grenade, and willl have a vacuum connection to the intake manifold, as well as a rectangular white electrical plug.

If they fail, they usually cause the engine to run really rich. You can check it by taking off the vacuum hose and suck on the fitting. If it holds a vacuum against your tonuge, it's usually still good. They are a pain in the ass to work with and $$$$ if it's bad. If I recall correctly, the ones for the 1.7L are NLA, but a 2.0L one will work with a little tweaking.

There is a test procedure for the electrical portion of the sensor, I think it involves checking the resistance across the terminals. Do a search here. I'm sure someone knows.

Another thing to consider is the AAR. I had a situation on my 1.7L where the car would not start due to the element inside shorting out intermittently. Took me a while to figure that one out. Unless you live in a REALLY cold climate, you really dont need it anyway. I just bypassed it, and the car started fine every time.

[Dave at Pelican Parts]

Sounds like you've got either a vacuum leak, or a throttle body that is really gummed up. Vacuum leak can cause a bunch of unpleasant running problems.

The "suck test" for the MPS will tell you if it is really very badly blown. A better test is to pull a ~15" vacuum on it with a vacuum pump (e.g., "Mityvac") and see if it holds for ~10 minutes or so.

You can see if the coils inside the thing are still connected by measuring the resistance through them, but you can't check the calibration with any reasonable hand tools.

Brad Anders has collected pretty much everything that is currently known about D-jet EFI, and posted it here: http://members.rennlist.com/pbanders

--DD

[MarkRobinson]

Well, I replaced most all the larger vacuum lines last night, & verified that my pressure regulator (the large grenade on the passener's side) does hold vacuum, however, my car generates about 100mm/hg vacuum: which is equivalent to about 5" where my 928 generates about 18" at idle. I got the same 100mm/hg both before my line replacement as well as afterwards.

Personally, I could draw about 400mm/hg out of my lungs (about 14-15" vacuum).

Where is the MPS? I finally found the AAR: down near the dipstick tube right? It has one electrical wire coming out from the bottom?

Thanks Dave, this forum is my pleasure.

Mark

[Dave at Pelican Parts]

The MPS is what you called the "pressure regulator", the hand-grenade thing on the passenger's side with one vacuum hose and one bundle of four wires plugged into it. The AAR has two hoses going into the top and one wire going into the bottom.

Not sure why you have such a low vacuum reading. What kind of compression readings do you see? Perhaps it's time to adjust the valves?

--DD

[MarkRobinson]

I haven't performed a compression check yet: engine runs pretty good, especially since last night when I saw that the throttle was only opening 2/3 of the way: adjusted the cable & the foot-stop, now opens 100%. You can hear the change in throttle (WOT vs cruising) now, where before you couldn't, & the car picked up a few HP at least (5 maybe?).

I do need to adjust the valves being that there are no records of it being done within the last 5-6 years, however, how do I test the AAR??

Thanks again Dave, You-da-man.

Mark

[MarkRobinson]

I've noticed that my trigger points (at the base of the disty) are probably original: since heat *could* affect them if there was a short or so in the wiring, how long do the trigger points last? I notice they're fairly pricy.

Im still not sure my stalling/bogging issue (ONLY when hot, engine runs smooth & perfect when the engine is not fully hot) is not related to the points. thoughts?

Mark

[Dave at Pelican Parts]

Originally posted by MarkRobinson
how do I test the AAR??

Easy. Find the hose that goes from the AAR to the air cleaner. Pull it off the cleaner and see if air gets sucked into it. When the engine is cold, air should go in. When the engine is warm (5-10 minutes of running), no air should go in.

...how long do the trigger points last?

The plastic "rubbing blocks" on the trigger points can and do wear. The electrical contacts just about never do, as they are passing a pretty small amount of current. Sometimes the springs on the trigger points get weak over the decades and they start to bounce, which leads to very rich running.

--DD

[MarkRobinson]

Ok, I'll check the AAR tonight: mine has a fine-guage red wire on the bottom (about 8" long) with a female splade terminal: that's it correct? However, if memory serves, it has two hoses to it: one to the intake manifold with a vacuum tee-off (about 2" long max), & the other hose goes to split in with the breather: I must have this incorrect.