308 QV ignition system

I know that you say that the fuel pressure is OK, but, the question is does the pressure remain at the correct levels at 3 minute, 5 min, 10 min and beyond after shut off as is required to keep the system from vaporizing the fuel in the injectors and lines. Did you check the return line from the accumulator for fuel? I found the same correct pressure but it would drop off after a few minutes even after I changed a bad accumulator. It turned out to be a bad check valve in the fuel pump. I added the external check valve at the fuel pump and changed the fuel line to match and it worked perfectly. The rest of the shotgun effect gets expensive.

Lots of luck

Dave

 

Hi Jan,

First - when the car won't hot-start, have you confirmed ignition (spark) is present? If not, this leads down a different diagnostic pathway. Engine in good mechanical condition otherwise?

Regarding fuel pressure, according to Probst's bosch FI book, "residual" pressure of 2.5b should be maintained for 20min when warm. If so, your accumulator is working, fuel pump check valve intact, and your injectors (nozzles) are not leaking. If pressure is not maintained, either accumulator could be failing, incompetent pump check valve, or injectors leaking.

Dave gave good advice. To this I would only add: if you have the fuel pump out, I would strongly consider changing the fuel filter ($12 US) and check valve ($13 US) if neither has been done in the recent past. I have the Bosch part #s (for 328) for reference if you need. Also have a pictorial on "How to Test Fuel Pressure" on a 328, happy to email if you'd like.

Having said all of the above, if you have a good mechanic I'm certain he/she has considered these aspects already. And (no offense) may know a bit more about specifics than you have posted. Again (no offense), unless egregiously in error, if you ask a shop to address a problem I would not second-guess their diagnostics.

Best,

Carl

 

I had the exact same problem with my 84 308GTB QV. After changing the check valve, fuel filter and accumulator it did not fix the problem (it did get a little better though). It turned out to be a rusty injector. What happened was that after the car stopped, fuel still flowed and caused it to flood. Right after I would shut the car off it would start fine but after 7 minutes it would not. If I let it sit for 30-40 minutes it would fire right up. Between the 8-20 time, it would not start, it would crank and crank until the battery was loosing power and then fire right up. It was only 1 rusty injector (I could tell right away when I pulled it) but I replaced them all and it is perfect now. Got the injectors for $8.00 each.

 

how long do you have to leave the engine off for the symptom to show up? If you can shut off the engine and restart almost immediately, then residual fuel pressure is more likely a problem, though not in this case if the mechanic checked things right.

if you see the problem quickly after shutoff, try unplugging the cold start injector plug. Also, remove the air intake hose and see if you smell fuel in the plenum. That would point to leaky injectors (doesn't seem likely if the residual pressure is ok), or a misbehaving cold start injector.

to check the thermotime switch, remove the plug at the cold start injector and probe the pins to verify you don't have zero ohms to ground on either pin when the engine is hot. You should see something low like 30 ohms on one pin..that's going through the thermotime heating coil...the other pin should be infinite. On my 328, the left pin is the infinite one.

if you suspect vapor in the fuel lines, try unplugging the blue plug from the fuel distributor and putting the key in the run position to run the pump a bit...may purge the lines. 'course, if you have a leaking injector, you'll probably be dribbling more fuel into the intake runner, but otherwise running the pump is no problem.

is the frequency valve buzzing?

unbolt the fuel ecu plate and check the relays on it for corroded terminals, and check the fuse on the oddball relay. Carl rose also has a nice write-up for checking other stuff on that plate (or sensors attached to that plate).

farther out in left field, check that the air plate in the metering head isn't gummy around the edges and sticking. Do that after the car has been cold a long time so there is no fuel pressure, otherwise pushing down the plate will dump gas into the intake.

if all that's ok, probably back to spark, which if you have a timing light or other form of spark tester, is hecka lot easier to check than some of the above

 

Where did you get injectors for $8.00 each?

Spang

 

AFAIK the 328 is similar (identical?) to a 308 in terms of ignition & injection systems. All I can tell you is that I've NEVER needed to floor the gas pedal to get my 328 to start hot or cold.

I know that used to be the remedy to get (any) carb'd cars to start but it shouldn't be necessary with FI.

At the risk of asking the bleedin' obvious, have you actually tried hot starting without flooring the gas? I just turn the key & catch it as it fires (which it does on the 1st/2nd crank pretty much every time). Could be you are just over fuelling/flooding the thing.

To be honest the routine to start the car is pretty much the same whether its hot, cold, wet, dry, inside, outside, etc etc !

I.

 

I have been trying to discover how the injectors come out, as you have replaced yours, can you enlighten me please.

 

Search the old fchat.com archives, there are several good descriptions of injector removal. BTW, They were mounted a couple of slightly different ways.

 

You have to pull the C-ring out to pull each injector. You can either use needle nose pliers or C ring pullers (very cheap at autoparts store). Use a flashlight and look down in next to the o-rings, you will see the rings right away. Once pulled, make sure to put tape over the holes!!!!! You also want to get some new ($2.00 each) rubber o-rings.

 

One thing that has not been mentioned, is an incorrectly adjusted airflow meter. If the Co adjustment screw is set too "rich" or "lean" the car will have a very difficult time starting when warm.

 

hi hugh,

assuming his car is euro (is it?), and it doesn't have lambda (does it?)....

if the mixture is off enough to create a hard start condition when hot, would there be noticable symptoms at idle?

if he does have lambda, and disconnects the O2 sensor when it's running and hot, would the car do something predictable?

I guess measuring the voltage coming from the O2 sensor to ensure it's swinging around 0.5V would confirm an ok base mixture...if he has an O2 sensor.

 

Hmm,
Usually a leaky injector will cause the fuel pressure to drop, not as fast as a bad accumulator tho.