I have had trouble starting my car lately. In trouble shooting it,
I have found that the fuel pressue at the rail pops up to about 30PSI
when the fuel pump initially runs before cranking the engine and then immediately drops back to near zero when the pump stops. It pops back up to about 30PSI while the engine cranks and stays there when the engine is running.

Let's assume the 30PSI is normal (may be an inaccurate guage or I may need to adjust it a bit).

1. Should the pressure regulator maintain the pressure in the rail at about 28 PSI even when the pump is not running or is my regulator bad?

2. I have checked all the sensors and checked the function of the intake air bypass valve (controlled by the engine heat). They seem fine. I have to crank it 3-4 times to get it to start and even then, it does not run at the higher cold start RPM it used to (where-in as it warmed up, it dropped in speed as the by-pass valve closed down). Ideas?

jrk

jrk, mine has been doing the same thing for five years. I just turn the key 3 times to build up pressure before I try to start the engine and it fires right up. But if you want to correct the problem, I would suggest checking for leaking injectors. and the cold start one also. bob

I just replaced two of them. I'll pull the rail and look for leakage but it is a dramatic dropoff and I suspect the real culprit is the fuel pump check valve.

Thanks for the input.

The pressure should stay at 28PSI after the 2-3 second system priming. The problem is almost surely the one way valve integral to the fuel pump. Its part of the out flow nipple and can be unscrewed for replacement(assuming you can find a good replacement.) The pressure regulator at the fuel rail is most likely good because its restricting fuel flow to maintain the pressure while the pump is running. Although I have never seen such a thing, perhaps there is a one way check valve you could install just a few inches forward on the fuel pump outlet side

The funny business with the PSI is what Ira said - a bad check valve in the fuel pump. But it creates a very subtle delay in starting when failed - only a second or so, not the 3 or 4 attempts at starting mentioned here. Frankly - I wouldn't bother trying to fix the check valve - its not your problem. Eventually the pump will go out and you'll get a new check valve with the new pump.

Something else is probably causing the hard start. Is this cold, warm, or both? Does a quick press of the accellerator pedal (triggering extra injector squirts) help it come to life? How did you check the sensors?

Also, before looking at the FI system, I've usually found it beneficial to make sure the other components are in proper tune as they can mask or create problems with the FI. Adjust the valves, check and clean the plugs, set the timing before tinkering with the FI. When you check the sensor readings with a multimeter my technique is to pull the plug off the computer and check the readings there. If you get a bad reading check at the component too - this will tell you if the fault lies in the wiring or the component.

I also wouldn't worry about the 30psi vs. 28 psi. You can use the fuel pressure adjsutment to fine tune the mixture. The little knob on the computer box itself just fine tunes a special idle setting - and has no effect on the off-idle mixture. A little time spent driving it hard, pulling/checking the plugs and tweaking the fuel pressure will get you to the proper mixture setting. Although - this is rarely very far from 28 psi unless the engine has been modified (displacement, cams, better breathing) and its fuel requirements have changed.

I agree that this should only cause a momentary hard start condition.
It is on cold start. After the 2nd try I can get it running if I work the accelerator. After about 15 seconds of nursing it, it will idle, roughly, at a slower than expected RPM, until it warms up a bit.

I have been using the FI manual I found refered to on this site. Wonderful document. Checked the function and values for the sensors based on that. I have not checked at the controller which is the best way and probably my next step. I have replaced the engine temp sensor (the front one). Plugs look OK. Wires OK. Timing on. Valves are OK.

I think my very next step is to check the contacts in the throttle position switch. It may not be getting the proper "I'm at Idle" signal.

Thanks for the support as I work through the bugs.

Jeff Kerr

Could be the cold start gas jet. It squirts extra gas into the manifold while cranking a cold engine. When it doesn't work a couple of stabs at the accelerator are needed to richen the mixture and start a cold engine.

It is the 5th gadget hooked up to the fuel rail - a short hose and its mounted on the intake manifold. The wiring goes from the starter itself (powered when the starter is engaged) then to the thermoswitch which is screwed into the side of the block to the rear of the oil filter. They look rather large for the task they do - I think they screw into an adapter instead of into the water jacket? Then on to the jet itself.

You can test this on a cold day with a cold engine by pulling the jet off the manifold and seeing if it squirts when the engine is cranked. If it doesn't follow the wiring upstream to find the problem.

I know first hand that a malfunctioning cold start valve can make cold starts nearly impossible. My early production E (early '71) uses a different setup - the cold start valve is directly controlled by the computer. The computer went out once and I was unable to locate this much rarer version, so I had to use a later model brain which doesn't have the cold start functionality. A somewhat compensating factor is I found one of those old adjustable mixture boxes once modified and sold by IPD. So I turn the mixture up to +30% on a cold start. That and a couple of judicious accelerator pedal pushes usually works. Then as it warms I turn the mixture back down. Its sort of like a hi-tech electronic choke. (I can also turn the mixture to -10% on steady low throttle freeway driving for better mileage).

I have checked the cold start injector in the past. Seemed to work fine. I had replaced the thermoswich also. I'll check it again. I replaced all the rubber booties on the connector ends and probably should go through the sensors/connections again to verify I didn't lose a connection somewhere. This hard start problem was present prior to my replacing the booties so don't suspect that highly.

jrk: You mentioned having replaced the "booties" on your FI system plugs. Could you let us know where you got those. I need em bad.

I got mine from Swedish Classics Incorporated, www.swedishclassics.com, 800-258-4422, part number 973693k. 10 piece kit. fit great.