78 No-Start w/out Fuel Priming

[rossiz]

i was pretty sue i was dealing w/a hot-start issue, as my current problem only commenced with hot days, hot running and the car would start beautifully when cold. i even waited for several weeks to log many starts prior to posting in the "hot-start" thread, but it seems this car is making me look a fool yet again (no difficult task, i must admit)...

the past 2 days my presumed hot-starting issue has become an every-start problem, even stone cold, first thing in the morning.

it goes like this:

turn the key, it fires up for a millisecond, dies immediately and will not start no matter how long i crank unless i prime the fuel lines. i do this by pulling the solenoid wire from the starter, turning the key to start and letting the fuel pump run for 10 sec or so. i've watched/listened/sniffed for leaks during the priming and starting drill, but i find no trace of fuel escaping. when i run the pump, i hear what sounds like air being purged through the system for about 5 sec. then it quiets down to just the sound of the pump and fuel rushing through the lines and the car will fire right up. once started, the car runs fantastic - no hesitation, great power, dead smooth idle, perfect.

new/replaced parts:

• fpr
  
• aar
  
• csv
  
• all vacuum hoses
  
• all sensors at the thermostat housing
  
• all injector plugs
  
• all rubber fuel lines in engine bay except the short ones between injectors and rail
  
• afm
  
• k&n cold air intake
  
• wires, cap, rotor, plugs
  

egr is removed, manifold plated off

i ran 2/3 can of seafoam through it a couple weeks ago to try and clean the injectors and de-carbon - sucked it in slowly through a vacuum port with idle set up high, let it sit 10 min. then fired it up and burned it off. this seemed to smooth out my idle - it's dead solid now, was hunting a little prior.

i have a fuel pressure gauge between filter and rail, it shows i'm holding 30+ psi, and when i prime (turn the key to run the pump) i can see it blip up a couple psi as the pump runs and drop right back down to 30-ish psi.

picked up a new fuel filter, plus a replacement for my clear inline filter between tank & pump (looks pretty nasty already after a couple months) but i don't think these are related, as i figure if it was starving for fuel it wouldn't run so well.

seems like i'm getting air in my lines, or at least that's what it sounds like i'm purging when i run the pump. at first i thought it was vapor from the hot-start issue, but i would think this vapor wouldn't stay in the lines after the engine had completely cooled. i have to do this drill just about every single time i start the car and it's getting old...

any thoughts?

[Zed Head]

new/replaced parts:

• fpr
  
• aar
  
• csv
  
• all vacuum hoses
  
• all sensors at the thermostat housing
  
• all injector plugs
  
• all rubber fuel lines in engine bay except the short ones between injectors and rail
  
• afm
  
• k&n cold air intake
  
• wires, cap, rotor, plugs
  

i have a fuel pressure gauge between filter and rail, it shows i'm holding 30+ psi, and when i prime (turn the key to run the pump) i can see it blip up a couple psi as the pump runs and drop right back down to 30-ish psi.

any thoughts?

Even though your engine does eventually start and, apparently, runs well once it starts, the 30+ psi is out of spec. It should be 36-38 psi when priming. That's not a huge difference but could be a factor. Or not.

It could also be that you have a vacuum leak and that plus the low fuel pressure is leaning out things enough to give a no-start. A small vacuum leak will have bigger impact at low RPM because it's a larger proportion of total air flow. You've blocked the EGR but maybe you missed a port, or the seal is not good. Maybe get the engine running and use some carb cleaner or starting fluid to check for a vacuum leak.

Have you adjusted the AFM spring, or installed a potentiometer in the coolant sensor circuit? That might compensate for the low fuel pressure during running but not the start problem.

Edited June 5, 2014 by Zed Head

[rossiz]

i'm going to replace the fuel pressure gauge - it's a fairly cheap hardware store pressure gauge and i'm not sure it's entirely accurate. but it's not reading any differently to before when there was no starting issue whatsoever. when the car starts correctly (which it did all winter, with the exception of some solenoid issues that were fixed) it literally fires up instantly - quicker than my newer/modern vehicles. blocked egr and afm adjustments were done back before starting problem occurred and it started/ran fine. no potentiometer in coolant sensor circuit, plugs look fine color-wise.

i will report back on the pressure readings from the new gauge and pull some vacuum measurements from the manifold, as well as do some starting fluid spray testing around the engine to maybe sniff out a leak...

[FastWoman]

Just something else to add to the equation: When you first crank the engine, if the temp is below that fuzzy 57-72 degF range, your CSV will be spraying fuel until the thermotime switch warms up enough to cut off the switch it off (probably a matter of numerous seconds). As a result your mixture changes quite a lot over the first numerous seconds of cranking, going from very rich to perhaps rather lean. And then if you prime your system without physically cranking the engine, the CSV might be accumulating a puddle of fuel into the intake manifold, resulting in a super-rich condition, and that might be what kicks the engine over. It could be, as Zed suggests, that your no-start condition relates to an incorrect mixture. Try unplugging your CSV to see if that makes your no-start condition go away. Also try spraying enough starter fluid into the intake to start your car after it has sat, and see if that gives it a big enough kick that it runs on its own after the first couple of seconds on ether.

FAIW, when I prime my fuel rail, I hear bubbles rushing through and clearing until the fuel pump sounds even out, and yet I can start my engine even before the bubbles have cleared. I have no idea where the bubbles come from.

[rossiz]

ok, so i found and fixed quite a few things:

• replaced fuel filter between tank & pump - it looked like an old coffee filter...
  
• replaced the main fuel filter in the engine bay - brown filth drained out of it
  
• replaced the fuel pressure gauge - it had been lying to me, stuck at ~30 psi reading even disconnected :disappoin
  
• replaced the efi relay with a spare i had - it was being flakey
  

so far it's started several times in a row w/out the priming routine - i'm thinking the filters were restricting flow, and priming was eventually building enough pressure to start. the new pressure gauge only goes up to 60 psi, so the scale is much wider and easier to read. it also moves much more smoothly. the system holds pressure for as long as i stand there and watch it, but it had bled out during the 2 hours when i went in for dinner...

tomorrow will be a big test.

[Captain Obvious]

I was going to provide a general public service announcement about pressure gauges in the fuel line. Goes like this...

My car wouldn't hold pressure when I shut off the car so I installed a pressure gauge in the fuel line. I found and fixed my problem which turned out to be my empty check valve back at the pump.

But I liked having that fuel pressure gauge up there, so even after the work on the car was done, I just left the gauge installed. Over time (two weeks or so?) my pressure started acting weird again. Sometimes it would jump around, sometimes it would be lower than it should be... So I started digging into the fuel system again.

Not finding anything wrong, I swapped the gauge out for another one and come to find that the original gauge was flaky. Took the flaky gauge apart to discover that the little brass gears inside had worn teeth to the point that sometimes they would skip and completely mess up the readings.

It's the hydraulic pulsing of the injectors. That little couple psi instantaneous blip you see on the gauge when the injectors open? It eats gauges for lunch.

I assume that there are gauges that are designed for this type of application, but the cheap little ones are clearly not!

On the topic of the issue you're having... Lets hope that the new filters take care of it!

[FastWoman]

Captain, I would think the greater sources of wear would be punching the throttle and engine braking, which would cause the gauge to swing back and forth quite a lot. I'm a bit embarrassed to say my cheapo Chinese gauge is still working fine. Maybe I don't work it as hard. Or maybe it's like that little, made-in-Macau plastic toy airplane I bought my son when he was a toddler. When you pulled a trigger, the propeller would spin. That crappy little plastic toy put in several years of very hard service without breaking. Incredible!

[Captain Obvious]

Right. I should have mentioned that it depends on the internal design of the gauge.

My gauge was pretty cheap as well, but it was a Bourdon tube style and had an internal linkage that involved gears.

You can go another level cheaper to gauges that don't use a Bourdon tube and are a direct drive style without linkage. Your cheapo Chinese is probably that ultra simple design. So by going that cheap, you accidently lucked into a design better suited for the application.

I made the mistake of using too good of a gauge on mine and paid the price.

[rossiz]

so i believe the fuel filters were the issue - the car started flawlessly in both cold (first thing this morning) and hot (several times throughout a hot day).

you guys were right that it was a lean condition. i checked the plugs and they were reading quite a bit richer just from today's driving, so i cranked back the afm a few teeth and the exhaust smelled a bit better as well (i've been known to sniff a tailpipe or two in my day).

the new fuel pressure gauge is much better. i opted for a whopping $15 gauge vs. the $4.95 special previously used, but price aside i think a real difference is the psi range. the old one went up much higher, i think 120psi or so, and the new one only goes to 60psi. this makes the scale much wider and easier to read, plus the needle sweeps a lot more distance, smoothing out the reading considerably. i like it.

the system holds pressure for a while after shutdown, but an hour or so later and it's bled off - didn't seem to make much of a difference though.

of course now my radiator is pissing all over the pavement, but that's a tale for another thread...

[FastWoman]

I remember my old '75 280 being EXTREMELY hard to start from a lean condition. I didn't have the hot-restart issue, BTW, but then again, I didn't have 10% ethanol gasoline either. But cold starts were really, really hard. I largely corrected the problem by repairing a bent vane on the AFM (bent from backfire).

Sorry to hear about your radiator. My advice: Don't get too fancy. All those cheap, aluminum racing radiators you'll see on ebay tend to be leaky, poorly fabricated things. The best replacement, IMO, is OEM-style.

Oh, and another project to add to your list: Clean out the fuel tank. You don't have to get too heroic about it for now, but you might at least drain the crud: Wait until your tank is nearly empty, park your car on a tilt (driver side higher), and drain the crud out of the tank through the drain plug. Jumping around on the bumper should keep the crud moving towards the hole. You can always filter the gas and return it to the tank, sans crud.

--------------------------------

Captain, I think my cheapo gauge is Rossiz's $5 variety. For all I know, it's stuck, and I'm fooling myself that it's not. Maybe that's why my fuel rail holds pressure so well!

Edited June 7, 2014 by FastWoman

[Captain Obvious]

Cool. Another crisis averted. My experiences are that as long as the fuel pressure holds long enough to crest the hot shut-down hump, then additional time is nice, but not required. An hour should be enough.

But what the heck? Now the radiator? Can you please get a two week trouble free stint out of that car??

[mjr45]

Hey, it took me 2.9 years to get a 2 week stint on my 75.