95 Riv hard starting only when hot

Hello Gents,

My daughters supercharged 95 starts great when cold, but cranks lots to start when warm after sitting a bit.

Fuel pressure regulator seams to be working right.

Any suggestions?

Thank you

redbaron wrote:

Hello Gents,

My daughters supercharged 95 starts great when cold, but cranks lots to start when warm after sitting a bit.

Fuel pressure regulator seams to be working right.

Any suggestions?

Thank you

Wondering how you tested the FPR - please elaborate.

By the way...if that FPR is original, or a replacement more than 2 years old, I'd replace it anyway and see what happens. There is a reason the replacements are cheap - because they don't last all that long. In my experience if you don't have a Delphi or Bosch FPR you're kinda hosed after a couple years. (easy tell - the good ones are made of stainless steel. The rest are yellow chromate coated. If you have a chromated one just replace it). I've gone through 2 Standard FPRs, neither has lasted more than 2 years. The replacement Bosch FPRs I've actually pulled out of junkyards, they have lasted 5+years each for me. The one I have in now was pulled out of a 200-something Park Avenue with the SC3800.

Other than the FPR, sounds like a fuel pump or (highly unlikely) fuel filter problem. Do you know how to test for those?

Dear Eleanor,

I tested the fpr with a pressure gauge when cold. disconnecting vacuum agreed with correct operation.
Was the prime suspect.

I agree with you on replacing it.

I'll let you know how it goes.

Nice Car!

Thank you
Joe from PA

96 Riv daily driver

redbaron wrote:

Dear Eleanor,

I tested the fpr with a pressure gauge when cold. disconnecting vacuum agreed with correct operation.
Was the prime suspect.

I agree with you on replacing it.

I'll let you know how it goes.

Nice Car!

Thank you
Joe from PA

96 Riv daily driver

The other test, Joe, is drive the car to warm then stop the car and pull the FPR. It does not take long, as you know you just need snap ring pliers and a good grip on the little can to pull it out of the fuel rail socket. See if you can drain gas out of the vac side of the FPR. If so, chuck it and install a new one.

When the FPRs that I have had went bad, the car acted like it had a bad fuel pump. But jumping the fuel pump, it ran fine cold or warm. What is happening is that the FPR fills a bit with gas as you're running, which fools the fuel system into starvation. Turn off the car and let it cool, the fuel bleeds back outta the FPR. Wash, rinse, repeat.

Pretty much any parts store FPR will work at first but again, they die *quickly* so what you can do is go ahead and get one then buy a good one off RockAuto.com or at a GM dealer, or even take your chances on a junkyard pull (just read the pressure rating off the little can). But be careful. The dealer lists a GM 24506988 at $157.- but it's for the NON-supercharged Riv. It will run and cruise more or less OK but it is the wrong pressure and you'll notice in highway passing or freeway merges. Really, you want the 3.8 Bar unit. The Delphi FP10377 is the one you want, it is a 3.8 bar unit. FYI One that will fit is for the Mercedes 300E, but it is a 3.5 bar unit, which is 100% OK for the non-supercharged engine on the Riv. Their # is Y0280160593 for the 1992 - 2005 Merc 300E. Bosch (the OEM for the Riv's fuel injection) is kinda like GM in that they don't create with impunity any new designs for hard mechanical parts. Like an FPR.

Hi Albert,

I did already purchase a FPR from Rock Auto. Didn't have time yet to install.
Hoping Saturday.

Thank you again for this valued information.

Joe

redbaron wrote:

Hi Albert,

I did already purchase a FPR from Rock Auto. Didn't have time yet to install.
Hoping Saturday.  

Thank you again for this valued information.

Joe

bump

what's status?

Hi Albert,

I realized I needed a 90 degree snap ring pliers.
Got one. Amazon
Am planning to install Saturday.

Thank you

Hello Albert,

I replaced the FPR Saturday.
My daughter didn't have trouble starting until today.

Back to square 1 again I guess.

The fellow I bought the car from last year said the fuel pump was new.
Not sure if I should suspect that.

Thank you
Joe

redbaron wrote:

Hello Albert,

I replaced the FPR Saturday.
My daughter didn't have trouble starting until today.

Back to square 1 again I guess.

The fellow I bought the car from last year said the fuel pump was new.
Not sure if I should suspect that.

Thank you
Joe

Your daughter's 95 Riv is almost 28 years old, and on cars it's not unusual to have multiple systems fail at this age. Some parts are engineered for "life of the car" but for most cars that's 10 years/150,000 miles or so. Some are engineered for more.

So... you are not back to square one; you did get some improvement. But... Did you ever measure fuel pressure at the fuel rail? Did the guy you bought the car from ever replace the crank sensor?

Albert,

I did inspect fuel pressure. Looked good.

I agree the crank sensor makes lots of sense... Behind the harmonic balancer right?

Thank you for your help!

Hope you have a blessed Easter.

Joe

Albert,

I did inspect fuel pressure. Looked good.

I agree the crank sensor makes lots of sense... Behind the harmonic balancer right?

Thank you for your help!

Hope you have a blessed Easter.

Joe

redbaron wrote:

Albert,

I did inspect fuel pressure. Looked good.

I agree the crank sensor makes lots of sense... Behind the harmonic balancer right?

Thank you for your help!

Hope you have a blessed Easter.

Joe

In the spirit of the holiday, I tried to think of the "one-time" or rare maintenance stuff I've had to do on my car.

- regasketing from the lower intake manifold out.
- brake booster check valve
- radiator
- front and rear sway bars (broke both after upgrading to Moog Problem Solver end links)
- rebuilt HVAC head unit (relamped it twice)
- factory exhaust (replaced a replacement with a new factory "onesie")
- replace pivot pins in tilt wheel mechanism
- drivers and passenger door latches
- drivers and passenger door window motors
- thermal breaker for power seats (until I figured out why it kept fusing)
- water barriers (behind the door cards) in both doors
- power antenna (twice)
- cam sensor (just for maintenance, it didn't fail)
- crank sensor (this was **so** difficult to figure out the first time. Twice. )
- drivers' side window switch cluster
- fuel pump (which if you keep at least 1/4 tank of fuel at all times, will probably run forever. Less than that they overheat and die)
- passenger side rear ashtray (remember those? The door spring on one failed. Never figured out why.)
- drivers side sunvisor (broke the end using it as a sunglass holder. Replaced it. It is still a sunglass holder I just don't horse it)
- exterior door latch handles, once each side

The seat hides are outstanding if you keep them cleaned and conditioned. Almost 25 years, no rips, no busted seams, no cracks. (Some character creases over the years ha ha)

Albertj

Albert,

Finally found time to change crank trigger.

Is good now.

Thank you and thank God!

Joe

redbaron wrote:

Albert,

Finally found time to change crank trigger.

Is good now.

Thank you and thank God!

Joe

You're welcome Joe.

The first time my crank sensor failed, I had to tell the service manager at my friendly GM dealer to replace it "customer request." They had tried various things that didn't work - my sensor had gone intermittently bad warm. So they'd fix something they could find, give me back the car, and it would then quit on the road to East Gybyppe or some darn out of the way place. I'd read about the problem and insisted they replace it - my risk, 'customer request.' They replaced it with a Standard (Blue Streak).

I was not as surprised as they were (mostly relieved), and that sensor lasted two years almost to the day. The next time they replaced it they used a Delphi; still running on that one. I remember having the car towed in for that one. They had learned a good bit about the crank sensor failure by then and had found the Standard sensors were not all that great. An issue with the electrical connections on the Hall sensor in the device separating inside the sensor housing after many many heat-cool cycles.

No scan tool, not even the factory Tech II or whatever, will show crank sensor failure on the Riv. This is because of where the sensor signal is reckoned in the startup sequence. If there is no signal, the fuel pump won't turn on b/c the computer thinks the engine is not turning, and the car won't start. If the car is running and the signal drops, the car will usually stall and stop because it looks to the computer like the car's been in a major accident or the operator has turned the key off (as reckoned by crank signal disappearing, which this car uses as a 'heartbeat.'). Specifically, if no crank signal the powertrain computer kills the fuel pump, whether or not the ignition +12v is present. The heck of it is, there *is* an OBDII code for this -- the dirty secret is, that code pretty much never trips because of the powertrain computer's order of operations. My guess is that if that code ever was triggered it'd more likely be a wiring problem, not the sensor per se.

Based in part on my experience with the crank sensor, that service manager and one of his techs came up with a way to use NOID lights to determine if the crank sensor is bad. That was after my first one failed around 2003 I think. Their approach has spread by word of mouth etc. Here is a relatively recent writeup using a version of their approach: https://dannysengineportal.com/crankshaft-camshaft-position-sensors-function-failure-diagnosis/ - it's a quick read.

For me it's pretty simple. No-start and everything else for a start is OK? Crank sensor original and more than 6 years old, or a replacement more than 2 years old? Eh, you might should replace it. At least, it's time to test it with a NOID.

Albertj