308 Hard Start when warm

Although you don't have a cat, does it have an O2 sensor mounted in the exhaust stream somewhere and an injection ECU (item B) and a fused protection relay (item C) like in the jpeg added somewhere?

On the US version V8 models using K-Jet with Lambda, +12V power for the injection system and the frequency valve follows the same rules as the fuel pump -- so your modifications must be a little different since you get the FV buzzing with the key "on" and the engine not running (although this has no bearing on poor hot restarting behavior).
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Thanks again for your interest and help. I realize this doesn't have anything to do with the hot start issue, but I definately would like to know exactly what I have and haven't got under the hood of my car. Like I said, this car is new to me, as is K-Jet stuff. The last few years I have been living in the land of the S.U. carburetor and Lucas electrics when it comes to cars, but I am catching on to K-Jet pretty quick I think, with help from great folks like you!

I went and crawled around under the car, and I can find no O2 sensors in the exhaust. The car has true dual exhaust, i.e. a completely separate system for each bank. I could also find no ECU like the one pictured. Where would it likely be located? I will attach a picture of my engine with what I am assuming is the frequency valve circled. The buzzing is coming from the circled part, and yes, it does do it with the key in the "on" position.

One thing I noticed is that the wiring to the circled part has some of that modern plastic, slip on wire loom stuff around it. At some point in the past the car had a Viper alarm system installed, and all the wiring associated with it has the same material covering the wiring. Maybe this valve could have been installed as part of the alarm system? I am just guessing here (since I don't know what a frequency valve does), but could it somehow cut off fuel supply and thus disable the car, and maybe this is why it would have been added with the alarm?

Thanks again for all your input, I really do appreciate it!

Nathan
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Circled part could be an after market FV. And what or where is that pluged hose with a blue bolt go to?

 

I could also find no ECU like the one pictured. Where would it likely be located? Nathan[/QUOTE]

The j-peg would suggest that it is underneath the floor of the rear compartment, mine wasn't. I had a 85 QV and the 2 x digi plex units were under a panel on the left hand side of the rear compartment. Closest to the coils etc.

 

In the 328 the marelli digiplex is under the panel on the left side of the boot. The ecu is under a panel on the right hand side. The picture shows the ECU from the right hand side.

Cheers

Mark

 

Well, you posted an interesting topic that hasn't come up before

A K-Jet with Lambda system without an O2 sensor is functionally really no different than your stock K-Jet without Lambda system -- so other than "looking" like it's been somehow converted/federalized, what's happening at the injectors best-case can't be much different than the stock euro set-up.

Since the FV is buzzing, you must have some sort of electronics/ECU rapidly switching the current on and off -- if you can't follow the wires from the FV, some other places where you might have a look for added electronics are under the seats or behind the passenger footwell panel (I doubt that FV is part of an alarm system and the common wiring covering more likely just indicates that the alarm work and injection system work was done at the same time by a shop using those materials).

If you can answer questions A & B in the jpeg, we might be able to draw some further conclusions and deduce what you have:
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Hoses #1 and #2 do connect to the same point on the WUR. Hoses #3 and #4 do not connect to to the tank. They connect to two separate fittings on the fuel distributor body.

Also, someone asked where the hose from the blue fitting went. The blue fitting is connected to the air filter box, and runs to a Purolator filter (see pictures) mounted on the rear firewall. Anther hose then runs from the filter, around to the front side of the engine compartment, to the metal tube that runs behind the engine, and then into a hose that ducks down heading towards the fuel pump area. I am not sure where this connects to, as I have not had the car on a lift or jackstands yet, but from feeling with my hands I THINK it is just vented to the air.

I took some more pictures of the areas in question to try to help everyone out.

Let me know if there is anything else than needs clarification. Stuff like this is what makes Ferrarichat so great!

THANKS AGAIN!

Nathan
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Good photos! Actually I believe hose #3 is directly connected to the tank since its banjo fitting shares the same banjo bolt with the return line to the tank (hose #4 also eventually connects to this return line via a valve inside the FD that is held open only when system pressure is present) -- could you please confirm/deny the supply line and return line labeling that I added to your jpeg.

My thoughts:

On the stock euro Mondial8 stock system (K-Jet without Lambda), the control pressure in Hose #2 is determined solely by the WUR (and the control pressure determines how far the plunger moves -- hence how much of the fuel slit is uncovered for a given incoming airflow).

On a stock K-Jet with Lambda system, the control pressure in Hose #2 is determined solely by the WUR, and the FV alters the lower chamber pressure inside the FD to change the pressure drop across the slits (which adds or substract fuel for the same slit opening).

On your system, the control pressure in Hose #2 is determined by the WUR and the FV acting in parallel (the WUR and the FV are both essentially controlled "leaks"). Although in theory this could work OK, it would really require modifying the internals of the WUR (to account for the nominal "leaking" of the FV).

Consequently, I think your best approach to investigate what's going on would be to measure the control pressure in Hose #2 to see if it's reasonable compared to the WSM spec -- should be "X" bar when cold and "Y" bar when warm (I don't have the specs but someone here will) and see if it does something strange at shut-off -- like immediately dropping to zero (which is what would happen if your FV isn't perfectly sealed/closed when unenergized).
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WOW. The knowledge being dispensed here is incredible! I will check out the other two lines you had questions about tomorrow...I had planned on jacking the rear of the car up and checking the brake pads anyway, and I will follow those lines on out then. Just by looking from above, however, I think you are correct in saying they go to the fuel pump/accumulator and tank return line. I will confirm tomorrow. I will also try to figure out where the wires from the FV are coming from. I pulled up the trunk carpet today and there are no computers there.

In any case, it looks like this is not the optimal set up. I am assuming it was done as part of federalizing the car when it was brought into the US in 1984. Anyhow, I am a big believer in things not being any more complicated than they have to be. Would there be any benefit in returning to a stock euro setup? Perhaps for no other reason than simplicity/reliability? And if so, what all would that entail other than removing the frequency valve itself? Is it something you would recommend?

The previous owner told me he "rebuilt" the WUR, but did not mention changing it internally. I am 99.9% sure this modification with the FV was done before he got the car, but I will call him and check. He recently replaced a lot of the fuel hoses, connectors, and other rubber bits, and said he replaced all the seals and gaskets in the WUR as part of that.

 

Alright 91TR, I figured I'd find you one more clue for this little detective mission we have going!

I just went out to the garage to do some last minute poking around before going to bed. I was trying to follow the wires from the FV and followed the loom those wires run in to the rear right-hand corner of the engine bay, where they felt like they were going into the trunk. Lo and behold, cleverly hidden behind the power antenna was this little device. It is labelled an FAC-1 Fuel Control Unit for K-Jetronic, made by DC Johnson and Associates, Inc. in Laguna Hills, CA. Hopefully this is some rare prototype unit smuggled from Maranello in the dark of night that suddenly makes my car worth millions, but I am not holding my breath on that one.

Is there any way this was some sort of performance upgrade? Or likely done just do get the car into the country? My car does feel nice and strong once warmed up, and I would not want to loose any of that. Lord knows us Mondial 8 guys need every last horsepower we can get! If there was no potential performance loss, I think I would like to revert to factory specs. What is your take on this?

I really can't thank y'all enough....I definately will owe some F-chat favors after this thread is all said and done!
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Eliminating the FV and that ECU and going back to just a stock K-Jet without Lambda set-up would be a more straight-forward situation (and no difference in engine power if everything was working right and tweaked correctly), but you're still left with verifying that the control pressure would be OK (i.e., confirming that the WUR wasn't altered in some fashion to account for the presence of the added FV).

The only advantage to that modification is that it clearly appears as a modification -- so could be helpful in BSing that the car is properly federalized on resale in some parts of the US, but, without real (O2 sensor) Lambda feedback (nor cats), it really isn't.

I'd confirm/deny the control pressure behavior with your existing set-up when cold, warm, and at shut-off, before deciding what to do next (i.e., bad behavior might make a stronger case for going back to the stock euro set-up, but, if you have proper control pressure behavior now, going back to stock euro won't make any difference at all).

 

That sounds like the best course of action. I know I said I am a big believer in things not being any more complicated than they have to be, but I am an even bigger believer in "If it ain't broke, don't fix it".

Can you recommend a reasonably priced pressure tester, and where I can find one at? The Sears here has a Crafstman fuel injection pressure gauge, but I do not know if it will fit the various ports on the Mondial.

 

Just do an internet search on "Bosch CIS tester" -- should get you several suppliers with kits in the $50~70 range (I've got the JC Whitney one).

 

Nathan,

That is a aftermarket frequency valve and "Johnson Box" it was put there to help meet US emissions standards when the car was imported. I think the state smog laws in MS are very lax like here in AL, so all you need to do is put it back stock and it will run better. If you call me I can go into more detail about what you need to do.

Larry
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Thanks Larry, I will definately be giving you a call this weekend.

91TR- I found a fuel pressure gauge kit I will be ordering next week, I am sure I will have more questions when I get my hands on it!

Question for today: Is there any way a leaky or improperly functioning FV can cause hot OR cold starting problems?

 

I can absolutely guarantee, that almost everyone on Fchat's grandmother, if your over 35 and if she drove, operated a manual choke on a carb, and started carbed cars when warm. Your gramma's couldnt spend 40 minutes shopping at Piggly Wiggly on a hot July day and not come out to a hot carb start. Yet very few women back in the day had any trouble getting old Betsy running.

On ANY carb engine, even a weedeater. The drill:

Cold engine. Okay, there is cold summer, and then there is really COLD! Bubba, ya'll wouldnt know bout that down there. Lets say 30 - 100F with cold engine.....

No choke, crank, add choke while cranking. Or on cars, dont choke at all, but pump. Only do not pump until your cranking. Dont have to go to the floor, most any carb give's a full shot of accelerator by half pedal. Any more just adds more air. I found that good running cars will idle cold after only a few seconds without any choke. But they generally need more throttle and a higher running speed. On a 308 with carbs, the fast idle cam on the water crossover should do that for you.

Warm engine. DO NOT CHOKE. Give half throttle and hold there as you crank. If it fires a bit and fizzles, let go and give half a pump. If it fires, give it some more.

HOT engine. Floor it, then crank while you continue holding to the floor. Dont let up till it fires. If it wont fire after 10 or 15 seconds, give a light pump and try to floor it again.

Starting a carby is a test of wits and skill. You have to out think the engine and carb. Did it boil off the fuel and its flooded, or is it just stagnant overheated fuel that wont burn? Do you pump it or floor it? Will the battery die before the engine kicks? Will I end up push starting this SOB? But in any event, if it fires, keep the revs up above 1500 and dont let it quit. Especially if its REAL cold, like below zero, or youll frost the plugs. Let it stabilise a few seconds and slowly drop the revs down as you massage the throttle with shots of accelerator.

I always try first to just crank it without doing anything, cuz ya never know. Sometimes they just pop. At the very least you just cleared it and you know it wants more gas. Now its a guessing game. The more familiar you get with particular engines, the more you know how to start them, but the general rules above work pretty well with any engine, even an airplane. You always want to go with the minimum fuel mix to get it running. If you pump a hot motor 20 times you can pretty much guarantee its flooded. Pull the plugs and burn em. But if you start off lean you can always keep adding til she pops, then you know your close.

Super cold start. I remember starting my Dad's 440 Chrysler for him one morning up in Duluth. Temp was -39F indicated on our store bought thermometer, but radio said -46F up on the hill, -42F downtown. Of course the high yesterday was like -28F, so it wasnt like it cooled down a whole lot. At those temps you got one shot to make it happen. Mess it up and you aint going anywhere. Dont turn on the key and waste any battery, just open the door quick and close it behind you, make sure everything is off, like the radio, and dont let that dim dome light suck up any extra power. Pump, pump, pump, turn key to on, pump & crank and hold key as you let off the gas. Squeeeeeeeeeewhirrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr rrrrrrrrrrrrrrrrrrrrrrr rrrrrrrrrrrrrrrrr

It didnt sound very happy, but it ran. I was just 14, and that was over 35 years ago, but thats the coldest I ever started an engine. And it wasnt plugged in or on a charger or anything, just cold as a dead horse. I'll take hot starting over that any day.

 

I saw this K-jet pressure gauge kit on ebay, and was wondering if it was a decent one, or some POS knock-off?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=300124839152&fromMakeTrack=true&ssPageName=VIP:watchlink:top:us

 

it'll work. For what to do with it, see carl rose's writeup here:
http://ferrari.cdyn.com/carl_rose_docs/Ferrari%20328%20CIS%20Fuel%20Pressure%20Check%20with%20Pixs.pdf